height problem with my prusa and slic3r

Hello,
I am in the process of calibrating my Makergear prusa I2. When I slice a 20mm calibration cube (20x20x10 with 0.9.9 slic3r) printrun tells me the following in the log.

the print goes from 73.460000 mm to 106.540000 mm in X
and is 33.080000 mm wide

the print goes from 73.460000 mm to 106.540000 mm in Y
and is 33.080000 mm wide

the print goes from 0.600000 mm to 10.400000 mm in Z
and is 9.800000 mm high


I don`t really understand why slic3r does what it does. I think the width of the object should be around 26-28mm (6mm distance from object and 2 loops brim)
The hight is another story. The object should be 10mm, not 9.8. The print should also start at Z 0.35, not 0.6.

Does anyone have any idea what could be causing this problem? I`ll upload my configuration in case someone wants to take a look at that.

I just learned the start height isnt an issue, its because the first layer height is 0.25. (0.25 + 0.35 = 0.6).

Buzz is an awesome guy and just explained to me why everything is right

First layer height is .6?

Slic3r is correct because the print distance is from all sides i.e. 2 x 6mm