"Can't very well use magic when your wand is out of bullets." - Homestuck
“If, by some strange coincidence, a hundred sharp pencils I was carrying embedded themselves in a third-party, would that be an accidental death?” - Nisemonogatari
There are 16 damage values for each ID and many more than 16 kinds of potions.
Quote from Lord Penguin »
That confirms they all use the same ID plus metadata.
"Damage" is used as the variable in the Level.dat for the Secondary ID of Blocks/Items in your inventory. It is a Signed 16Bit number meaning it goes from –32,768 to 32,767 rather than just to 16(Even when its used for damage it goes higher than 16, it goes into several hundred at least). Damage and "MetaData" are the same thing.
Quote from smiley face 177 »
It doesn't show splash potions yet, just edible potions.
Splash Potion ID's were added to Minecraft Info a few days ago. "Normal" Potions ID's were updated(For some reason the older Potion ID's used in early Pre 1.9 Beta's still worked though they couldn't be used to create Splash Potions).
Regarding it, if you say /give ???? 373 you will get a water bottle. The commands are easy since its simply like this /give ??? 373:16418 and you will get a swiftness II splash potion, its really hard to tell though. Though I am using TMI, all of the potions have different ids, like it lasts long or its short, so hard to tell.