The current phrasing contains the same information but is a bit harder to interpret:

Computed from 4000 by 262 log-likelihood matrix

ParetoSmooth.jl is more explicit about this, with a phrasing that mentions "n observations and m posterior samples." I've found this prevents mistakes -- it's very common for users to accidentally misspecify what it is they want to leave out, e.g. by placing all their observations in one multivariate normal, which causes confusion when the whole dataset is left out. I think this might be a more useful message.