Amending with an additional W-2: different results if just added and in amend mode?

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Discovered an additional W-2 (long story) for 2023. 

If I am adding it to our already submitted return, it recalculates without any errors and federal tax is about $700 more (makes sense) and state is 1715 more (again makes sense).

Once I switch into "amend" mode, federal tax goest up to $830 and state to $1699 ($16 less).

No other amendments were made. 

I've assumed that interest or some penalty is automatically added, but no.

Total income to be taxed is the same in both scenarios, already paid taxes the same as well.

What could possibly be the reason for additional $130 and what can I possiblly check?

Thank you!