Have been scientifically proven*** to be the number of years a guy would extract from his real age when he is uncomfortable with revealing his actual ‘maturity‘.
So when he said he’s 34, he’s actually 41.
When he said he’s 25, he’s actually 32 with a daughter.
When he said he’s 22, he’s 15. (Yes, it works the other way around for under 25s.)
***By scientifically proven we mean experienced by at least a gay and a straight encounter from at least 3 different nationality and 2 different age decade.