NDN on Nostr: Might be a dumb question... But why is the total bitcoin supply such a random number ...

Might be a dumb question... But why is the total bitcoin supply such a random number when the block rewards have always been a multiple of 5? Will the end result be a nice even 21000000? Example below from latest block

{
"height": 851002,
"bestblock": "000000000000000000011617f028ae6bb7cad63a6b12ac9c00f489e78ab6056d",
"txouts": 185753675,
"bogosize": 14303832579,
"hash_serialized_3": "310d1be993209488a0e76dd1906bd4063ef01b17fa52ac3fe4ad255f4fc596a2",
"total_amount": 19721664.86691132,
"transactions": 128213191,
"disk_size": 12472526707
}