Hey Walid,
Sorry for the incomplete report/question. I was typing on my phone as I was at the machine about to run a job.
Let me explain.
I understand WHY you choose to use G91, but the Min & Max values on the Job description don’t know the difference. I was trying the surfacing generator (which is awesome, by the way) to clean up surface after an epoxy pour. My plan was to only take off 2mm. When I was about to start the job, I happened to notice that the Min Z height was -4mm. Taking an extra 2mm off would ruin the job. Almost gave up, but then I saw why it was doing this. Even when I understood the WHY, it was a bit nerve racking to run a job that said it would go deeper than I wanted. Of course everything worked as that -4mm was a relative move, but I think you can see the issue.