Adtech ADTECH9 Series Programming Manual page 66

Function
Before cutting starts, make tool radius compensation (usually XY plane) action at the position before leaving
the workpiece, and then Z axis can execute cutting; at this moment, Z axis motion can approach the workpiece
quickly, and then executes cutting action, which contains two sections; please pay attention to the description
below:

Example:
When programming as below
If above program, i.e. N1 compensation starts, pre-read to N6 segment, and then determine the relation
between N1 and N6, and compensate appropriately as shown above.
Then, divide N4 segment into two in above program.
At this moment, there is no instruction segment of XY plane in the four continuous segments N2-N5,
pre-reading isn't allowed from N1 to N6, and overcutting as above occurs.
Basic execution compensation is made with N1 only, but correct compensation vector can't be made, and thus
overcutting occurs.
In this case, considering the calculation in NC, in the cutting direction after Z axis descends, before Z axis
descends and cuts, and add the instruction of the same direction to prevent overcutting.
N2 and N6 have the same direction, thus the compensation can be executed properly.
ADTECH9 Series CNC Programming Manual