SSDI Lump Sum

Hi...In 2020 I received a "Lump Sum" of $5971 that I was owed for years of under payments. My 2020 SSA-1099 only lists the amounts for 2016 thru 2019 ($2220), then there's a line that has "$3559 paid in 2020 for other tax years". When I am entering the years and total in the Wages & Income>Lump Sum I really only have the actual amounts for the four years listed and a breakdown for the other $3559 which probably covers another six or seven years.

Do I have to itemize the years with totals? If so does anyone have any idea how I can get the data from Social Security for the many years not listed on my 2020 SSA-1099?

Thanks