AP Practice Exams: Are they accurate?

So yesterday I took an AP Bio practice exam from 2014 at my school under real-test conditions (timed and everything) and got a 4. Our teacher told us that the real exam has more questions, though.

Will this reflect how well I will do in May, or are practice exams not accurate?

Well if the sample of questions isn’t biased (taken from a few categories only) then it should be a decent predictor.
Best indicator would be a previous AP test.

The actual exam has 63 multiple choice and 6 grid ins as well as 8 free responses. For the 2014 exam, I heard somewhere that they put in 10 multiple choice and 1 grid in field testing questions, so it actually comes out to 53 points. If this is the case, then I hope they have field testing questions for every year.

sorry, I meant 58 points above