File sizes in iTunes are still in Mebibytes not Megabytes
The file sizes displayed in the "Size" column, and in the "Status Bar" at the bottom if more than one track is selected, are still showing Mebibytes, whereas the Finder displays file sizes in Megabytes ever since Snow Leopard was introduced in August, 2009.
If you insist on display Mebibytes then you should use the correct abbreviation of "MiB" (not MB) after the size figure to save confusion. Or you could follow Donald Knuth's proposal and use the MMB suffix.
It would be more consistent to mimic the changes to Finder and correct this. Otherwise users might get confused when the Finder tells them they have enough space on a Memory Stick or external disk drive to copy some selected track(s) but when they try to do so then the copy doesn't fit. For instance, Finder says the destination has 21.0 MB available, iTunes says the selected track is 20.1 MB, and the copy fails because it is really 20.1 MiB which is actually 21.077 MB.
The best way is to just alter iTunes to display true Megabytes (1,000,000 bytes). If it was a good idea for Finder then it's a good idea for iTunes, even if it is 5 years late. 😎
iMac, OS X Mavericks (10.9.5)