I'm somewhat inexact. I usually do them about 20 to 25 mins on Meat/Stew or Steam and usually I'm busy with something else and I leave them for at least a few mins before doing a quick release. I like to put apple juice + a bit of apple cider vinegar in the Instant Pot with them and sprinkle a bit of S+P on the ribs themselves before they go in. Then I brush with sauce and finish them in the oven at 400F for at least 10 mins - I like them browned a bit.
I was also going to try this recipe with a double-rub and the IP. His recommendation is 20 mins on steam, leave for 5 mins then release.
Edited to add: 15 mins + slow release is probably just fine. You'll get that extra little bit of cooking time with the slow release and they are less likely to fall apart on you when you take them out. Sometimes, mine are falling off the bone a bit too soon...
