I have a Sieg mill and Mach 3 running Ok but when I go to the Offset screen the documentation talks about the touch buttons and doesn't mention the select buttons.  If I try and set G54 with an edge finder and enter the diameter of the edge finder, save the settings, then jog the axes away from the current positions then press goto zero on the program run screen the tool zeros to my required work offset origin but it has not allowed for the edge finder diameter.  What am I doing wrong?    

find the edge with your edge finder,  Zero axis move Z up then move axis half the diameter of the edge finder, then rezero axis.  Set g54 after compensating for half the dia. of the edge finder