Page 4 itself is a lie. Social Security has never been a pure Pay as you go system, though it was for a long time "mostly" a pay as you go system, but that changed drastically in 1983 in the Saint Ronnie and Uncle Alan supported reform. Benefits this year, and in future years, can be paid from current taxes and from accumulated trust fund assets.
And, page 5 proves this point, with all that lovely sexy revenue exceeding costs.