They, maybe, should calculate that with "half-point". If the rule is the next one :
Skills points per level : 2+(0.2*Intelligence).
- 3 points each level for 5 in Int.
- 4 points each level for 10 in Int.
They could gives half-point like :
- I have 6 in Int, so i gain 3,2 skills point per level. So i gain 3pt each level and 4pt at level 6 (3,2+3,2+3,2+3,2+3,2).
Then a guys which is improving is Intelligence must be reward by all the skills he loses from the beginning, in fact the difference between the new score and the old score.