Well, Matt said Stick left twenty years ago. When Stick left him, we know Matt was older than nine, so ten at the youngest. If he's thirty in 2015, that would put him at 25 in 2010.

Maybe Foggy and Matt got jobs after high school and went to college later? Foggy's family seems working class ("It's not every day a Nelson breaks from the ranks of hardware and cured meats.") and Matt's inheritance from his dad might not have been enough to put him through school.