This sequence terminates at exactly 247 moves which is the point at which the blue-cell's work is complete and the glider-gun will naturally evolve. The LWSS can be seen moving east towards the bi-block. To complete the formation of the glider gun just move the blue-cell glider away (say to the north-east, starting U/SS/SS/SS/SS...) and retire it.

Again, because of the length of this sequence I recommend you avoid using the undo button which can be very slow. Instead use Undo All and then Redo to explore the sequence forwards from the beginning.