How I trim mine & for my daughter is to shoot them a few ends to get a beginning crease in it where it feels right on your hand, then I'll get a marker & grip the string with the tab on & mark just beyond my finger tips.
Cut the excess off from the area marked then shoot some more.
I'll trim a little here & there on the tab to finish it because I like mine where I have just a little over wrap on the string but not much to catch the string on some of my better releases :rolleyes: but it still does the job of protecting my fingers.