I received $61.21 less than was submitted on my adjusted 2020 tax return. How can I find out why?

When I filed in February, I owed over $900 for Federal Tax.  When the new tax law passed, my CA unemployment that I received for 6 weeks was declared tax free.  I filed an adjusted return with Turbo Tax, but I got my IRS check today and it's for less than shown on the Turbo Tax adjusted 2020 return.