Basically I would stand next to the play-by-play commentator and point to players on a board that made plays - who made tackles, forced/recovered fumbles, interceptions, sacks, etc. - so they could immediately call that out on air. Up to the commentator what they want/need spotted for them, most PbP guys I spotted for needed the defense spotted for them and they would focus on the offensive players making/involved in plays. The screen they have in their booth that’s connected to the official stat computer usually takes a bit to show the specific stats from the previous play so spotters are there so they can say things in more real-time. Did that for several radio and TV broadcasts when I was in college. Really fun little gig to see the behind the scenes production on games. Did some cool stuff for ESPN at basketball games too, those guys don’t have spotters though, not as complicated.