SEA-1099 lump sum payments.

How do I know which portion of reported income on my SSA-1099 is a one lump sum payment?

I am pretty sure that I received a higher one lump sum payment, than what is being reported on my SSA-1099 as lump sum payments. Should I report the amount I believe the lump sum payments to be, or only the years and amounts as reported on the document?