It is well established math. In each Monero transaction there are many possible senders and possible receivers, and while the amount of the transactions are not visible, you can prove that inputs equal outputs.

If x-y = 0 you know x = y but not actual transaction amounts. Monero supply audits verify that inputs equal outputs on all transactions. So not possible to know how much is where. Yes, there is a non-zero *unlikely* chance of an inflation bug. But an accepted trade off for L1 privacy.

It may take longer to detect on Monero due to obfuscated transaction amounts. But BTC hasn’t been immune to its own inflation bugs either.

Trade-offs. If you want to just Hodl forever then Monero may not be your best choice. However, if you want to transact privately without jumping the rough the 27 simple steps /s… then it’s a suitable option.