This is enough to Master 8 (out of 9) skills if you keep the last one in Basic (with 4 points) or you can Master 7 skills and have the last 2 on Advanced. That means when each trainer can teach you 1 skill point, you can get 40 + 4 + 40 = 84 skill points. There are 4 or 5 trainers for each skill, total 40 trainers.
Level limit is 40 which means you get 40 skill points from leveling and you have 4 skill points from racial bonus. You have 9 skills each with 10 points needed to master it -> you would need 90 skill points to master all skills. Let's confirm that by some math (warning for minor SPOILER): However, it seems it's correct that you can ask each trainer only once and the bug is that there is no message saying 'you already trained with this trainer'.
