Refer to spreadsheet, it has answers for most questions you'll have with skills: https://docs.google.com/spreadsheets/d/1MXQkApC-pAJjPaIlWevRR_BBad4noowlGJeQJyEtwM4/edit?usp=sharing

For these three... Impacts, Double Impact, and Triple Impact all belong to the same type of attack known as Pursuit attacks.

• Impact - 20% chance to deal an extra-hit of 18% - 20% of damage.
• Double Impact - 100% chance to deal an extra-hit of 18% - 20% of damage.
• Triple Impact - 100% chance to deal two extra-hits of 22% - 25% of damage.

Keep in mind that these activate per base hit of the attack, and the damage they deal is based off of the final damage of the base hit.

So for example, let's say your attack deals 4 hits:

• 1st Hit: 400 damage; Impact Procced and dealt 72-80 damage; Double Impact dealt 72-80 damage; Triple Impact dealt 88-100 damage twice.
• 2nd Hit: 500 damage; Impact didn't proc; Double Impact dealt 90-100 damage; Triple Impact dealt 110-125 damage twice.
• 3rd Hit: 400 damage; Impact didn't proc; Double Impact dealt 72-80 damage; Triple Impact dealt 88-100 damage twice.
• 4th Hit: 500 damage; Impact procced and deal 90-100 damage; Double Impact dealt 90-100 damage; Triple Impact dealt 110-125 damage twice.

These Pursuit attacks won't overwrite anything because they're really completely different attacks. There's also not just these 3 skills that are in this category of attacks, and it's possible to stack some crazy amount of hits with them. Very fun stuff.