I am confused on how CLEP and DSST tests are graded?

I read people saying they received a 65, 48 50 ect and passed. My confusion is for example, 100 question test, if you miss 30 out of the 100 you would get a 70 (C). I am guessing it does not work in that manner.
Is it say, out of 100 you must get X number correct? and incorrect answers don't count, so when saying "I received a 55" is that they had 55 out of 100 correct?
I am finishing up my BS with a b&m school by taking these last two class using DSST.
I just want to ensure I have all the bases covered so I can finish.

Thanks
Sgtwillys

120 credits finished and had this double minor idea, so that is why I need two more classes. Just to think I could have been done now, AHHHHH