Answer, basically it depends on whether your MB unit is 1000^2 or 1024^2.
Let me explain:
If you look at a file online and the site states it is 15.5 MB and then you download the file, verify the hash, and notice Windows states the file size is 14.7 MB, one might wonder what is going on.
Windows considers 1 MB to be 1048576 bytes. 1024^2
In my particular example the website considers 1 MB to be 1000000 bytes. 1000^2
Therefore (truncated, not rounded)
15507456 bytes / 1000000 = 15.5 MB
15507456 bytes / 1048576 = 14.7 MB