There are around 5000 airlines with IATA codes.
IATA airline designators [..] are two-character codes [..]
after an airline is delisted, the code becomes available for reuse after six months
The last quotation suggests that no two airline companies can share the same IATA code.
Depending on the characters allowed, a two-character codes can make $26^2=676$ combinations or eventually $36^2=1296$ combinations. It would take at least 71 different characters authorized to register 5000 companies ($71^2=5041$). It is unlikely that 71 or more characters are authorized. It seems paradoxical to me.
What am I misunderstanding?