G76 thread

Hello everyone, I searched a lot around here but I didn't find my answer.  I'm trying to cut a thread in G76 and I didn't understand why I put a 3mm pitch (P=3) to be able to make the pitch I wanted which was P=1.5, and I understood that my lathe is making two thread entries.  I couldn't understand this, could someone help me?

2 thread entries (multi-start thread) most probably means that your index signal is happening twice per turns. The fundamental requirement for threading is that you need one and only one index per turn.

Also, is your scaling right for the Z axis? This is easy to check by comparing the measured distance of travel vs the commanded distance.

The Z and X scale are correct I checked and the spindle index is ok too