Notice that button has only $81 left after his flop bet.

PokerStars No-Limit Hold'em, $2 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

SB ($198)
Hero ($365)
UTG ($199)
MP ($261.60)
CO ($161.65)
Button ($127.25)

Preflop: Hero is BB with J, J.
UTG raises to $8, 2 folds, Button raises to $24, 1 fold, Hero calls $22, UTG folds.

Flop: ($57) 7, A, 9 (2 players)
Hero checks, Button bets $22, Hero raises to $341