IRS reduced the federal refund amount and I don't understand the reason

I checked the Federal refund tracking site and found a notice the refund amount had been reduced by what looks like stimulus checks [$2,400]. They will automatically deposit the balance by Mar 22. I used Turbo Tax and had it do all the reviews and checks of entries with no problems. 

The reasons they gave in their 'details' window listed five different potential reasons for the reduction. Some of them are just silly. Based on the dollar amount of the reduction I suspect it has to do with stimulus checks.

I have PDF files of the reduction notice and the 'details' notice.

How do I get some support from Turbo Tax to help me understand what went wrong?