Duration issue - audio, .m4a

[ghender3]

I have tried using Lossless Cut as an audio editor for iTunes .m4a. I have noticed this issue: if I select all, and export, the duration of the exported file is generally some fraction of a second shorter than the original file, as shown in MediaInfo. In fact, MediaInfo gives both Duration, and Original Duration. And the total number of samples is a lower number.

I have also noticed that if the original file is Apple Lossless .m4a, there is is no change in either duration or number of samples.

Could anyone tell me if the change in duration for iTunes .m4a would "technically" change the pitch, or whether the change is just a removal of part of the file? And would anyone know whether the removed material would be at the end or beginning of the song?

Thanks for looking