Is it one stun token per damage point before armor or one stun token per hit regardless of amount of damage before armor ?

One per hit, as long as the damage (before armor) is greater than zero.

"After inflicting at least 1 damage (before applying the effects of armor) to a figure with a Stun attack, place a stun token next to the figure."

So, my giant does 7 points of damage before armor and 3 points of those 7 get through characters armor, then the character gets 7 stun tokens ?

No. The character will get 1.

Dlanaan said:

so, on the very next turn the character loses the stun token (if only receiving one) like it did not happen (since the monsters attack was last turn) ?

cbytes said:

Yes.

cbytes said:

Not "like it did not happen," since Stun tokens still affect you during the turn they're removed. The hero will only get a "half-action" (move your speed, attack once, or place an order) instead of a full action (advance, battle, run, or ready) on that turn.

cbytes said:

Stun tokens on a hero actually have no effect. It is the act of removing a stun token from a hero that has an effect. Read the stun description carefully.

This is similar to Bleed tokens (only have effect when they are removed, although all get removed at once rather than only 1/turn) and completely different from Burn, Daze, Poison and Curse tokens, which all have ongoing effects as long as they are present.