4th job Single Target DPS

I find a similar formula about dual element charge..

1 when Paladins have dual charged, they attack with dual element too.
2 lighting : (125% - 100%) / 2 = 12.5%

How it works? for example:
Paladin with 140% fire charge and 125% charge,
for a normal mob, it is 140% + (125% - 100%) / 2 =152.5%
fire weak, 140% * 1.5 + (125% - 100%) / 2 = 222.5%
lighting weak, 140% + (125% - 100%) / 2 * 1.5 = 158.75%
both weak, 140% * 1.5 + (125% - 100%) / 2 * 1.5 = 228.75%

in calculate order, it is A class modifier.
All we knows is 12.5% not 125% or 25% ,so we need a Level 1 lighting Charge Mage to help testing

Edit：
I washed the 3rd job skill of my paladin and hurried to do a test. Lots of cash
I get two skills: Lv.7 Fire Charge:Mace, and Lv.2 Lighting Charge:Mace for testing.
Here's the test report.

 Spoiler

Paladin Str:890 Dex:69 Watt:105
weapon:two handed mace, mastery:15%
Base Damage: 501.3855~4558.05
prostrate Damage: 99.30375~503.475 (I use this formula once more =w=)

Buff:
Lv.7 Fire Charge:Mace, 112%damage
Lv.2 Lighting Charge:Mace, 104%damage

Mob:
pdd:20 none element weak.

Test Damage Range:102~561

Calculate:
A: 99.30375~503.475 * (112% + (104% - 1) / 2) - 20 * (0.5, 0.6) = 101.2~563.96
B: 99.30375~503.475 * (112% + 104% / 10) - 20 * (0.5, 0.6) = 109.54~604.25, out of range

so the formula A is right.