Forum:The bason potion

In book 7 we learned the timeline of this location for the Horcrux.

1. Voldemont visit the cave with Kreacher and the following happened.

1. Vold made Kreacher drink all the potion.

2. Vold put the locket into the bason.

3. Vold REFILLED the bason with potion to protect it.

4. Vold left and then Kreacher left.

2. R. Black visits the cave with Kreacher

1. RGB made Kreacher feed him the potion and told Kreacher to destory the locket.

2. RGB drank all the potion and crawled into the water and died.

3. Krecher left and tried to destroy the locket.

3. Dumbledore visits the cave with Harry.

1. Dumbledore drank the potion and etc....

So the issue I'm having is after RGB drank the potion, it was never REFILLED. So there shouldn't have been any potion there for Dumbledore to have to drink. I suppose that it can be said the bason refills itself but that Vold wouldn't have to refill it after he made Kreacher drink it. Just seems like an oversight to me.