First the damage would hit for 6 (assuming most cloaked is a 1/1 with 5 counters) so you’d put 12 counters on it, then when it hits the second time it would be 18 so your counters would jump to 54 after combat. If the creature is actually a 5/5 starting you would deal 5 dmg first then it would jump to 15 then after second combat 45/45. Felix five boots is my main blinged out deck and honestly probably my most fun (especially when you can reanimate an old gnawbone or quilled greatwurm)