The numbers in cells are eXperience Points (XP) that go to corresponding skills. When you add a few drills in the schedule, you can see what amount of total XP goes to each skill. From your example: Positioning are going to get 0.41 XP (3% of total XP from this schedule), Shooting -- 3.25 XP (26%). ITP shows you what exactly your player is going to train with the schedule you've created. You can easily compare different drills to each other and decide which one you need.
Every skill gets +1% when accumulates required amount of XP. There're many factors that affects XP, both visible (i.e. age, stars) and hidden (so called Talent). So no wonder it happens sometimes player gets nothing from a single training, expecially if he's old and has slow training rate. But it may happen he gets +8%.