Hero power bug

[Venge]

I think there's a bug on Mistress of Ordenfell hero power,
 
I perfect evolve 1* lvl100 hero + 1* lvl100 slime = hero power goes 528 to 607 which means it added 79 power

then i perfect evolve 2* lvl1 hero + 1* lvl1 perfect slime = hero power goes 607 to 639
which means it only added 32 power

I think it's bugged because

1* + 1* = 0.000125 = 0.0125% of these stats are carried over to your final hero

2* + 1* = 0.0025 = 0.25%



3* + 1* = 0.05 = 5.0%


so the 2* + 1* should add more power than 1* + 1* evolution