Phil,
As Stu says, the professional monitor is a tool for mapping on the dyno with a system (such as P8) that can't be live mapped.

What you do is load the engine to X revs, check the A/F and then make adjustments on the monitor to get this right (either putting in or taking out fuel and / or ignition), making a note of the adjustments that were need to get the A/F spot on. You then reset the monitor so that it is back to zero (as in fuel / ignition curve exactly what is on the chip) and then repeat the process for each rev increment. Once you have done this, you adjust the information as per your notes for each increment, burn the chip, replace it in the ECU and then repeat the process at each increment to just make sure the adjustments made get the desired A/F. If not, then you just use monitor to adjust them up or down from the new "zero" point that the reprogrammed chip has at the relevent increments. Once fully completed, the chip can then be burned.

Obviously it can be done live as well, you just make the required adjustments on the monitor to get the desired A/F and then change that point in the map on the laptop to the "zero point" plus what you had to adjust the monitor to get the A/F spot on and then pull the lever on the dyno again to check it. You can then see why Pectel P8 takes a lot longer to map than doing it live...