diff --git a/stl.go b/stl.go
index 4c58cf9..a9f4498 100644
--- a/stl.go
+++ b/stl.go
@@ -444,7 +444,7 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Creation date
 	if v := strings.TrimSpace(string(b[224:230])); len(v) > 0 {
 		if g.creationDate, err = time.Parse("060102", v); err != nil {
-			err = fmt.Errorf("astisub: parsing date %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: parsing creationDate %s failed: %w", v, err)
 			return
 		}
 	}
@@ -452,23 +452,20 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Revision date
 	if v := strings.TrimSpace(string(b[230:236])); len(v) > 0 {
 		if g.revisionDate, err = time.Parse("060102", v); err != nil {
-			err = fmt.Errorf("astisub: parsing date %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: parsing revisionDate %s failed: %w", v, err)
 			return
 		}
 	}
 
 	// Revision number
 	if v := strings.TrimSpace(string(b[236:238])); len(v) > 0 {
-		if g.revisionNumber, err = strconv.Atoi(v); err != nil {
-			err = fmt.Errorf("astisub: atoi of %s failed: %w", v, err)
-			return
-		}
+		g.revisionNumber, _ = strconv.Atoi(v)
 	}
 
 	// Total number of TTI blocks
 	if v := strings.TrimSpace(string(b[238:243])); len(v) > 0 {
 		if g.totalNumberOfTTIBlocks, err = strconv.Atoi(v); err != nil {
-			err = fmt.Errorf("astisub: atoi of %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: totalNumberOfTTIBlocks atoi of %s failed: %w", v, err)
 			return
 		}
 	}
@@ -476,7 +473,7 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Total number of subtitles
 	if v := strings.TrimSpace(string(b[243:248])); len(v) > 0 {
 		if g.totalNumberOfSubtitles, err = strconv.Atoi(v); err != nil {
-			err = fmt.Errorf("astisub: atoi of %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: totalNumberOfSubtitles atoi of %s failed: %w", v, err)
 			return
 		}
 	}
@@ -484,7 +481,7 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Total number of subtitle groups
 	if v := strings.TrimSpace(string(b[248:251])); len(v) > 0 {
 		if g.totalNumberOfSubtitleGroups, err = strconv.Atoi(v); err != nil {
-			err = fmt.Errorf("astisub: atoi of %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: totalNumberOfSubtitleGroups atoi of %s failed: %w", v, err)
 			return
 		}
 	}
@@ -492,7 +489,7 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Maximum number of displayable characters in any text row
 	if v := strings.TrimSpace(string(b[251:253])); len(v) > 0 {
 		if g.maximumNumberOfDisplayableCharactersInAnyTextRow, err = strconv.Atoi(v); err != nil {
-			err = fmt.Errorf("astisub: atoi of %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: maximumNumberOfDisplayableCharactersInAnyTextRow atoi of %s failed: %w", v, err)
 			return
 		}
 	}
@@ -500,7 +497,7 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Maximum number of displayable rows
 	if v := strings.TrimSpace(string(b[253:255])); len(v) > 0 {
 		if g.maximumNumberOfDisplayableRows, err = strconv.Atoi(v); err != nil {
-			err = fmt.Errorf("astisub: atoi of %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: maximumNumberOfDisplayableRows atoi of %s failed: %w", v, err)
 			return
 		}
 	}
@@ -508,7 +505,7 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Timecode start of programme
 	if v := strings.TrimSpace(string(b[256:264])); len(v) > 0 {
 		if g.timecodeStartOfProgramme, err = parseDurationSTL(v, g.framerate); err != nil {
-			err = fmt.Errorf("astisub: parsing of stl duration %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: parsing of timecodeStartOfProgramme duration %s failed: %w", v, err)
 			return
 		}
 	}
@@ -516,7 +513,7 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Timecode first in cue
 	if v := strings.TrimSpace(string(b[264:272])); len(v) > 0 {
 		if g.timecodeFirstInCue, err = parseDurationSTL(v, g.framerate); err != nil {
-			err = fmt.Errorf("astisub: parsing of stl duration %s failed: %w", v, err)
+			err = fmt.Errorf("astisub: parsing of timecodeFirstInCue duration %s failed: %w", v, err)
 			return
 		}
 	}
@@ -524,16 +521,16 @@ func parseGSIBlock(b []byte) (g *gsiBlock, err error) {
 	// Total number of disks
 	if v := strings.TrimSpace(string(b[272])); len(v) > 0 {
 		if g.totalNumberOfDisks, err = strconv.Atoi(v); err != nil {
-			err = fmt.Errorf("astisub: atoi of %s failed: %w", v, err)
-			return
+			g.totalNumberOfDisks = 1
+			err = nil
 		}
 	}
 
 	// Disk sequence number
 	if v := strings.TrimSpace(string(b[273])); len(v) > 0 {
 		if g.diskSequenceNumber, err = strconv.Atoi(v); err != nil {
-			err = fmt.Errorf("astisub: atoi of %s failed: %w", v, err)
-			return
+			g.diskSequenceNumber = 1
+			err = nil
 		}
 	}
 	return
@@ -587,28 +584,28 @@ func parseDurationSTL(i string, framerate int) (d time.Duration, err error) {
 	// Parse hours
 	var hours, hoursString = 0, i[0:2]
 	if hours, err = strconv.Atoi(hoursString); err != nil {
-		err = fmt.Errorf("astisub: atoi of %s failed: %w", hoursString, err)
+		err = fmt.Errorf("astisub: hours atoi of %s failed: %w", hoursString, err)
 		return
 	}
 
 	// Parse minutes
 	var minutes, minutesString = 0, i[2:4]
 	if minutes, err = strconv.Atoi(minutesString); err != nil {
-		err = fmt.Errorf("astisub: atoi of %s failed: %w", minutesString, err)
+		err = fmt.Errorf("astisub: minutes atoi of %s failed: %w", minutesString, err)
 		return
 	}
 
 	// Parse seconds
 	var seconds, secondsString = 0, i[4:6]
 	if seconds, err = strconv.Atoi(secondsString); err != nil {
-		err = fmt.Errorf("astisub: atoi of %s failed: %w", secondsString, err)
+		err = fmt.Errorf("astisub: seconds atoi of %s failed: %w", secondsString, err)
 		return
 	}
 
 	// Parse frames
 	var frames, framesString = 0, i[6:8]
 	if frames, err = strconv.Atoi(framesString); err != nil {
-		err = fmt.Errorf("astisub: atoi of %s failed: %w", framesString, err)
+		err = fmt.Errorf("astisub: frames atoi of %s failed: %w", framesString, err)
 		return
 	}