Longstanding Rune bug (Scaling mana regen)

the mana regen per level blues give 0.06 regen per level = 1.2 @ 18 the yellows give 0.065 per level = 1.17 @ 18 this is weird as yellows are primary for regen. after doing some "very advanced math" i found that the actual values at level 18 for the blues was actualy 1.08 i don't know the actual effect in game. rito plz