Does the Fire Elementa’s Touch attack’s ongoing damage stack with itself? [duplicate]

If a fire elemental uses the Touch attack:

Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) fire damage. If the target is a creature or a flammable object, it ignites. Until a creature takes an action to douse the fire, the target takes 5 (1d10) fire damage at the start of each of its turns.

And then hits a creature twice, how would the emphasized text work? Would the creature have two instances of it and take 2d10 damage at the start of the turn or only one? If they would have it twice would they be able to put both out by dousing the fire?