Storage Quota measurement unit is GB (Gigabyte) or GiB (Gibibyte)? Provisioning discrepancy?

Hello, I am using the "Create user" api with the optional "space_amount" param. I see some discrepancies.

a. Why does Box UI represent storage quota in terms of GB (Gigabyte) instead of GiB (Gibibyte)? e.g.: When I create a user with 1_000_000_000 Bytes (1 GB), Box provisions 1_073_741_824 Bytes (1 GiB) yet in the UI it shows as 1 GB. Why so?
b. Looking at my attached table, if I request 1_000_000_000 Bytes (1 GB), Box provisions 1_073_741_824 Bytes (1 GiB). If I request 10_000_000_000 Bytes (10 GB), Box provisions 9_663_676_416 Bytes (9 GiB). Why over-provision for 1 GB request and why under-provision for 10 GB request?
c. Looking at my attached table, between Box accounts 1 and 2, for account 1, if I request 100_000_000_000 Bytes (100 GB) then the API response says 10_737_418_240 Bytes (10 GiB) but Box UI says "unlimited", but the behavior is different for account 2, if I request 100_000_000_000 Bytes (100 GB) then the API response says 99_857_989_632 (93 GiB) and Box UI says 93 GB. Both are enterprise accounts, what else can cause such behavior change between the two accounts?

Source: https://www.iec.ch/si/binary.htm