How to calculate Persuasion/Charm/Intimidate on a Persian? (Divinity: Original Sin)

By the way, once after reloading to the window with three answers, after each option (at the end in brackets) - the numbers of the change in the base option (3) were indicated. For example (0) or (+1). Either they are trying to add it in the new version of the game (I play 219), or it should have been a long time ago, only some bug does not allow them to be displayed.

Strength grants a bonus to your intimidation skill.
Intelligence gives a bonus to argumentation (persuasion) skill.
Constitution gives a bonus to charm skill.
Charm gives a bonus to all three options.