I got it…
I made a wrong assumption that LB would accept my A axis as being “Relative” which is not the case…
But moving my (50.265) line to 0,0, LB sends 360 to my firmware… I just needed to put the line (at Y=0) in LB 
It would be a nice to have in LB to be able to define A axis as relative… but meanwhile, I can modify my fw to cope with it 