When to start be concerned about wrong reporting?

I am seeing that Koinly thinks I have X amount of fiat on exchanges, while that’s not true.

How should I be concerned about that? I feel like it is potentially has other side effects that could be affecting my realised/unrealised gains and the overall tax reporting. But given that a lot of other things seems to be accurate enough, I am a bit confused.

Specially, if the system could occasionally have wrong calculations, how can I trust it not to show me wrong data and lead to wrong trading decisions that might cost me extra taxes?

Thank you