In the NHL, overtime (OT) is forced when two teams are tied in goal scoring after regulation time ends. Overtime is played in a sudden death format, which means that if a team scores a goal, the game ends, so there is no way a player can score more than one goal in overtime.
So how did Mr. Clowe manage this feat of scoring both goals in this overtime game? It wasn’t by magic. Clowe scored one goal in regulation and the other one in overtime; hence, he scored both goals in the OT win.