How much is left if theres 499 MB out of a 2 GB

1,501 Mb's if in decimal form (used for File Storage Space)

Basic math tells me: 2,000 - 499 = 1,501

To check this answer, we would reverse the problem as so:
1,501 + 499= ?2,000?

In terms of REAL AND VIRTUAL memory, 1 GB is actually 1024 Mb's, so 2 Gb will be 2048 Mb's. So if you are speaking about RAM, the math problem would actually be
2048 - 499 = 1549 Mb's

Hard Drive manufacturers base their storage space on the Decimal value, so when you go get a 80 Gb, for instance, your actual storage space for file's is only 80,000 Mb's when in all actuality, it should be 81,920. So instead of having 80 Gb's, you really only have 78.12(5) Gb's.