docs -g-code: add the amount of retract in g73 and g83

Author: c-morley

docs/src/gcode/g-code.adoc

@@ -1782,7 +1782,7 @@ the Z axis.
   ** Move to the X Y coordinates
 * Move the Z-axis only at the current <<sec:set-feed-rate,feed rate>>
   downward by delta or to the Z position, whichever is less deep.
-* Rapid up a bit.
+* Rapid up .010 of an inch or 0.254 mm.
 * Repeat steps 2 and 3 until the Z position is reached at step 2.
 * The Z axis does a rapid move to the R position.
 
@@ -2396,7 +2396,7 @@ with the addition of retracts during the drilling operation.
 * Move the Z-axis at the current <<sec:set-feed-rate,feed rate>>
   downward by delta or to the Z position, whichever is less deep.
 * Rapid move back out to the retract plane specified by the R word.
-* Rapid move back down to the current hole bottom, backed off a bit.
+* Rapid move back down to the current hole bottom, less .010 of an inch or 0.254 mm.
 * Repeat steps 2, 3, and 4 until the Z position is reached at step 2.
 * The Z-axis does a <<gcode:g0,rapid move>> to clear Z.