IF you set up work 0,0 to be the lower left of bed travel facing the front of the machine THEN all moves WILL be positive. WHere you setup Machine HOME is a totally different thing to where you work from. I see you refhome to the top left. that sets Machine zero as you say then all move in MACHINE corrds will be neg. BUT you don't WORK in machine coords you work in work coords.(;-)
Note my earlier statement IF your mill is a bed or knee mill it will move the axis BACKWARDS to a GANTRY setup for the same tool positioning. SO your setup cannot be the same direction wise to your gantry mill/router
Just a thought, (;-) TP