Added note and changed category in migration guide

Author: j04chim

docs/en/appendices/5-4-migration-guide.md

@@ -14,15 +14,6 @@ automating some of the migration work. Run rector before updating your
 bin/cake upgrade rector --rules cakephp54 <path/to/app/src>
 ```
 
-## Breaking Changes
-
-- `Number::toReadableSize()` now calculates decimal units (KB, MB, GB and TB)
-using an exponent of ten, meaning that 1 KB is 1000 Bytes. The units from the
-previous calculation method, where 1024 Bytes equaled 1 KB, have been changed
-to KiB, MiB, GiB, and TiB as defined in ISO/IEC 80000-13. It is possible to
-switch between the two units using a new optional boolean parameter in
-`Number::toReadableSize()`, as well as the new global setter `Number::setUseIecUnits()`.
-
 ## Behavior Changes
 
 - WIP
@@ -33,6 +24,15 @@ switch between the two units using a new optional boolean parameter in
 
 ## New Features
 
+### I18n
+
+- `Number::toReadableSize()` now calculates decimal units (KB, MB, GB and TB)
+using an exponent of ten, meaning that 1 KB is 1000 Bytes. The units from the
+previous calculation method, where 1024 Bytes equaled 1 KB, have been changed
+to KiB, MiB, GiB, and TiB as defined in ISO/IEC 80000-13. It is possible to
+switch between the two units using a new optional boolean parameter in
+`Number::toReadableSize()`, as well as the new global setter `Number::setUseIecUnits()`.
+
 ### Utility
 
 - New `Cake\Utility\Fs\Finder` class provides a fluent, iterator-based API for

docs/en/core-libraries/number.md

@@ -205,6 +205,11 @@ This mean that:
 - 1000 Bytes = 1 KB
 - 1024 Bytes = 1 KiB
 
+::: info Added in version 5.4.0
+It is now possible to use the byte units defined by the ISO/IEC 80000-13
+standard alongside more natural decimal units.
+:::
+
 ## Setting the Default Byte Units
 
 ### Number::setUseIecUnits()