I think there have been others who have stated incorrect intelligence calculations with the addition of equipment, but I could not find the topic thread...
In game 3968 ("3vs3", Westeros), my hero "Paul" is showing 82 intelligence on the "Abilities" screen and 127% with the equipment added on the equipment screen (which also shows the 82% as the base).
He has two items increasing his intelligence, the "Infernal Cranium" which gives +25 and the "Wizards Charge" which gives +20. I have put 2 ability points into intelligence, which should make the base 140 and with equipment 185...which is drastically different from 127%
It's not my turn, but soon will be, I did try playing around with unequipping and equipping again, but it makes no difference to my base int...they must be cursed items!