2^20 = 1.048.576 ≠ 1.000.000 = 10^6
Ki Mi Gi Prefixes are for powers of two, K M G for powers of ten.
Of course you can choose whatever prefix you prefer, but when talking about storage or anything digital, we usually mean the power of two series. For that matter it's better to be explicit instead of assuming everybody knows.
True, i misread your first post.