The blue number that appears is the bonus.
Effect: Converts 10% of your HP into SP. The higher the skill level the more effective the conversion will be. The conversion rate is 1:1 modified by SkillLV, so a 2000 HP Professor with Health Conversion LV 3 would gain 2000*10%=200 SP plus 30%, total 260 SP.
Level Description
1 10% More Effective
2 20% More Effective
3 30% More Effective
4 40% More Effective
5 50% More Effective
10% of 3870 = 387 plus...
10% of 387 = 38
20% = 76
30% = 116
and so on
If you reduce your sp to like half and use health conversion you'll notice that even though it says 78 in blue, you'll have regained more than that (387+77 being 464 at level 2).
