Exactly how does Illaoi heals work?

I've been playing Illaoi a bit lately, but I'm still not entirely sure how her Q works.

If it hits a champ, it restores 5% missing hp. But if one tentacle hits 2 champs, is that 10% missing hp? And if two tentacles hit one champ, is that also 10%? Then, getting more complex, one champ getting hit by 2 tentacles, then another champ being hit by one of the tentacles is 15% hp?

Thank you for your answer is you did :)