It tells the player how good a slaver is in a profession (list professions shown increases with more missions taken). for example, for the four new slaver, this list profession proficiency is zero, since the player hasn't taken any missions. But after the first quest, it shows how good the slaver is (maybe measured by score) in known professions : Planner and Builder, which shows up in the last mission. As the company takes more missions, this list of professions proficiency info increases, making it easy for player to decide which slaver to hire into the company, and which to fire if necessary to make room for more valuable slaver.

p.s. maybe also increases the limit of number of slaver. with how many variance in slaver's last professions, traits, skills, etc, it is such a shame to not be able to gather all kinds of slaver in the company. Though that's just my personal opinion