The offset click generator is only useful when you are trying to click a gump position and not for a world coordinate. You'll need to "click" the coordinates found by your character position and 2 spaces around.
For that you use you need to load the values of the ground position into #LTARGETX, #LTARGETY and #LTARGETZ as well as #LTARGETKIND (see EasyUO for an explanation of this value)
After that you just need to do a use last object (set to your shovel) and use last target because you've set the X,Y and Z values
I don't have a real good example. The ones I have are either WAY advanced and not obvious, or totally old and stupid.