It's an approximation, which might be completely useless to you when coding (ie. "Read a 2MiB chunk from a file" is different from "Read a 2097000 byte chunk")
It's written down in a longer form than it would be if it was just written down in decimal base, which makes it completely useless to use such a notation in this case.
Edit: seems like lemmy.ml is shitting themselves atm, excuse the multiple deleted comments