That is confusing indeed. There is another equation that has BaseArmorValue instead of ArmorHealth%, it's probably more accurate.
Lets say you have a skill of 75, Therefore: (0.35 + 0.0065 * 75) * 60 = 50.25
I'm not sure how much an additional armor health of 25% would add to armor rating but lets assume that it's just 25% more.
50.25 * 25/100 = about 12.5
ArmorValue with a skill of 75 is 50.25 + the 25% more health 12.5 = 62.75
Yes, I am terrible at math but I hope this helped