available space is displayed incorrectly

[Finn]

If I want to install a game there is a free space of 902GB but in Explorer it only has 882GB free space. How can I fix that Steam shows the correct storage space?

[nullable]

Unless you've got some setting configured I've never bothered to look at, Steam usually displays space in MB by default. 882GB converted to MB is 903168 MB which is close, and fudging the numbers a little between decimals and whatever rounding you or the system is doing does put this pretty close to what you might be seeing.

So I'm not clear if you're actually seeing a disparity or if you're confusing things by incorrectly converting units and being a little imprecise in your question.

[Bad 💀 Motha]

Nothing to fix, don't worry about it.

[Julien, cut it out.]

The radix is not 10, but 2.
This means f.e. that 2^10 = 1'024 byte is 1 kibibyte and not 10^3 = 1000 byte is 1 kibibyte.

For your calculation that means 1 gibibyte is 1'024 mebibyte.
So 902'000 mebibyte is ~= 880 gibibyte (902'000 mebibyte divided by 1'024 (mebibyte per gibibyte) ).