counter question/understanding

[Nexulo]

Hello and thank You for the excellent work!

I have a question about the usage of the counter parameter.

How is this parameter to understand?
Shouldn't the authentication of my YubiKey 5 NFC abort/prevent the login when i've manually changed the counter to a bigger or smaller integer in my database? The authentication only shows an error when i manually set the counter in my database to a bigger value as expected and after a few invalid login attempts, the login works.

I thought the counter in my database and on my YubiKey always has to be the same value (with a small fault tolerance)?

Thank you and best regards,
maisen20