Amended return

I received a corrected SSA-1099 and started an amended return. Before I changed any data TurboTax showed an additional refund of several hundred dollars. Have there been changes in the tax laws since early February 2021? If not why would I show an increased refund amount before making changes? I continued to update my SSA-1099 and when done my AGI increased by about $1000.00 but my tax liability decreased by a little more than $500.00. Just trying to find what has changed before I file my amended return. Thanks