What is this 10NL? What did he buy in with?

A Limp reraise is usually A,A, but if he came in half stacked and is 31/11 over a min of 100 hands I push to the rr preflop and expect to be ahead most of his range (quick estimate; A,A-9,9 prob.; A,Qo+, A,10s+, maybe a few more).