@lcattanach1
Once you determine the $$ amount that is from US Govt Obligations...
You then edit the 1099-DIV, and on the pages AFTER the main 1099-DIV form, you check a box indicating you have some US Govt interest for that 1099-DIV form, then enter the exact $$ amount on a subsequent page:
(See pictures below form the Desktop software...Online is similar)
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____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*