If the final beat in a gatra is a rest, the seleh is the last note played. It is not uncommon in gamelan repertoire to find entire gatras of rests. Note that the actual length of time it takes to play a gatra varies from less than a second to nearly a minute, depending on the tempo (laya) and the irama.
In gamelan music, if the final pulse is muted, the seleh is the last sound produced. It's not uncommon for entire gatras to be filled with silence, which can vary greatly in length from under a second to almost a minute, depending on the tempo and rhythmic feel of the piece.