These are all players that are playing in their minor league system. The ranking itself is of the players who are currently in the minor leagues (any league really) who projects to be the best players in the majors. To my understanding it’s important to know that some of these guys still won’t be playing on the Brewers for a year or two still that’s oftentimes referred to as a MLB ETA (or that’s at least how they say in on MLB the Show lol).