IRS gave a refund more a few dollars than I asked for. How do I account the difference when amending this return ?

That was probably for interest.  Just ignore it.  It will be taxable income next year.

That was my first thought.  After some internet search, my understanding is that IRS has to pay interest if the refund comes later than 45 days after the original deadline of 4/15. My refund came in mid March. So I don't think they need to pay any interest.

But since the difference is only a few bucks, I guess I can safely ignore it.