Postured up finish ufc 5

I see it show up when postured up on the ground to submit with l1 and r1 on the opposite side of the screen where transitions are, but I don't understand how to get it to come up all the time. Or how to use it. Every time it shows up it immediately disappears before I have a chance. What are the requirements to trigger it online.  I haven't seen it anywhere else in the game, only online.