Okay the way it works for me is if I'm really struggling to reach on VE then its -2 above i/s or if I can reach but abit difficult its -1 at the spines reach easy no probs can feel easil around head/cervix etc.. +1 and +2 are well on there way well +2 is basically sitting on perineum, thats how I do it-right or wrong? but it works for me.
On palpation we do how much we can feel of the head and basically divide it into 5ths (how cruel lol) so if you think you can feel alot of the head then we say its 4/5ths palpable or something along those lines x