Watch the episode where Joey and Chandler take Ross to the Rangers game to get his mind off his ex-wife. When the slapshot comes flying into the crowd, it hits ross in the nose. This always stops play (and the clock.) But when they are shown on the JumboTron, the clock is still running!
Being played on the jumbo-tron means that it is a replay not the actual game going on. So the clock still running is probably the replay of him on there. Or who cares about the clock it's just a t.v. show.