Hi
Your first mistake was to create things that are 'lifted'. SketchUcam does not work like that.
It is designed around FLAT drawings and adding cut lines around or inside those outlines.
(though it does have a 'generate 3D' mode that does a very rudimentary 3D carving, do not use this if the article needs to be the right size!)

To do what you want to do, you can approach it from a number of directions.
One way is to use copies of the master drawing, do the hole on one copy, do the pocket on another drawing, generate gcode for each one, run the gocde sequentially, or manually combine the files and run it all together.

You can achieve the same thing using groups, since groups can overlay each other without interfering (much).
Firstly never place a plunge hole intersecting a horizontal line, you can draw a positioning line to help find the center, so long as it is not horizontal. I do little triangles that are smaller than the bit size.

1 - draw the counterbore
select the plunge tool.
type 20 and press enter. this sets the depth to 20% of material thickness
hold down SHIFT and click the center of the hole
you are prompted for the diameter, enter 8 (I work in mm)
you see a circle and a purple horizontal line, select all that and group it.

2 - put in the center hole
select the plunge tool, the default depth is already set to your inside/outside overcut %
do not change this if you want the hole right through the material.
point at the center of the counterbore and click.
select the small circle and its purple line, group it. (you can give groups names under 'entity info' and the names will be visible in the gcode output. groups also affect the order of cuts so the read the help about the group reorder tool)

Now the gcode will cut the counterbore and then the center hole.

To get up to speed on using this plugin you really need to read the help (big blue question mark in the toolbar), and then watch the various videos linked from the install instructions at
http://www.phlatforum.com/xenforo/threads/sketchucam-download.3128/

Happy cutting

 

to quote the help for Phlatbones (big blue question mark in the toolbar!)

 

Some further info on counter boring:
since version 1.2a plunge holes are automatically grouped for you so you don't need to group them manually.
The auto grouping prevents background geometry interfering with the gcode generation EXCEPT
when there is a horizontal line from the center point extending to the RIGHT, ie, underlying the pink 'here is a hole' line.
However, after placing your hole, just delete the underlying line (NOT the PINK ONE!) and it will work just fine.

If you are not running the latest version of SketchUcam you should be!