Grading scale

Hello guys! I have been taking a bunch of practice test from different companies ETS ppp, Manhattan, and Kaplan. I notice that the grading of Manhattan is based on the difficulty of the question, even if I have 15 questions out of the 40 in quant I can ended up with 158 if most of those questions are difficult or hard level. Now I have read that the GRE also grades the same way, but my experiences with the PPP 1 and 2 is completely different, ETS and Kaplan are only giving me a single point for any questions regardless of the difficulty level. Will the Actual GRE will be that same as the PPP grading or is more like the Manhattan grading based on the difficulty of the question?

PPP1: 304

PPP2: 301

Manhattan 2: 307

Manhattan 3: 310

Kaplan 4: 302

Grading scale :

So, after reading the two links what I understand, is that the actual GRE rewards you more for answering a harder questions, but I haven’t experience that in the PPP 1 or 2. So do the practice exams don’t grade you as the actual GRE?

PowerPrep Plus seems to do that for me. I got a 164V and 164Q, but missed 8/40V and 7/40Q. If I understand the grading correctly I got a +2 to my Verbal and a +1 to my Quant.