Help with skill dmg

Hi,

I’ve created a new barb char to try to understand how skill dmg is calulated. The char is lvl 8 with 1 point in Charge and 1 point in Rupture. He’s naked but for the weapon and has no paragon allocated, ofc.
It’s stats are: STR 85, WepDmg 34-52 (43 mean), the weap is a 2H mace.

Charge Dmg bonus is 180% and Rupture is 13%
Now Charge dmg should read 1.8 x 34 to 1.8 x52 that is 61- 94 (rounded) but the game skill reads 75-92
For Rupturre should be 0.13 x 34 to 0.13 x 52 that is 4-7 (rounded) but it reads 5-6.

So the question is what am I missing? How is base skill dmg calculated?