It's a summary of teams' players at a given level and position. If you're looking at ML/SS and a team has a 4 under Count, that team has 4 players on the ML roster with SS as their primary position. Current Avg is the average current Overall rating of those players. Top Current the highest rated player at that level/position and his current Overall rating. It's a way to narrow down trade targets — if you need a CF, a trade is more likely with a team that has 3 ML CFs and 4 more in AAA than a team that has 1 in the majors and 1 in AAA. If you want to obtain prospects, you can set the level to all and sort by count to see who has a surplus at a given position.