Odd damage values for potions.

I'm working on a plugin that moves potions around, and want to insure that it's moving the right potions at the right times.

The issue I'm running into is that when I create a org.bukkit.potion.Potion in code using (for example)

Code:

(new Potion(PotionType.REGEN).extend().splash())

and check it's damage value, I get (binary) 0100000001000001.

If I create the same potion in game, insert it into an item frame, and then check the result's damage value, I get (binary) 0111111111010001 - 7 bits in the middle of the field have changed from zero to one.

So, my question is, why are those seven digits changing from zero to one, and should I ignore those bits when comparing potions?