Help with determining Creature DCs

[Cyussu]

I'm going to be playing in a game soon that the DM has allowed me to take a homebrewed class. But one of the monsters I have chosen to own has an odd DC that doesn't explain how it go to it. If someone would be ever so kind to assist me in such, I would be grateful.

Monster: Roiling Oil, http://www.d20pfsrd.com/bestiary/monster-listings/oozes/roiling-oil

Ability in question: Nauseating Film (Su)

The page says 9d8, but in the case of mine, it's a 14d8 Slime. The latter of the 2 is easy because it outright says "Constitution Based" but the 1st ability's DC is 2 lower.

[Remuko]

Hmm I'm not entirely familiar with pathfinder so maybe it has changed but in 3.5 the DC for a monsters abilities is almost always (afaik) 10 + 1/2 HD + ability mod + sometimes a racial or feat bonus.

However that 9d8 Ooze's Con mod is a 7 and half its HD is a 4 so the DC should be 21 for the 9d8 Ooze. Either PF uses a different formula or its a typo, I'm not sure which.

[Echch]

This might be wrong, but the ability mentions that it is a poison. Maybe it refers to an existing poison with a fixed DC?

Of course, Remuko might have a point and it was simply a typo. After all, it's other ability lists the DC at 21...