Bug on TurboTax or My Misunderstanding: I Bond interest taxed by state?

See screen shots - I bond interest should not be taxed by states. However, I am seeing $12 more tax if there is $1K more I-bond interest. The following screen shots are captured from TurboTax Premier. Is this an TurboTax bug? or is there extra tax that include Treasury bond interest for relatively high earners?

 

I bond interest $2,914 => Tax Due $1,410


Screenshot-2024-03-10-at-8-32-53-PM

 

I bond interest $3,914 => Tax Due $1,422

Screenshot-2024-03-10-at-8-31-54-PM