Geeetech

Hello there. First post.
I assembled an I3 full Aluminum kit and I am quite impressed so far with the results.
My problem is when it comes to holes or internal gaps. All my external dimensions are pretty much correct. maybe +-0.05 which is acceptable.
When I have a hole on the model, or a slot for a nut to fit in, the result is much smaller. Actually it is 0.6mm smaller. 0.3mm on each side which is my nozzle size.
Its like the software does not calculated it right.
I am using repetier and slic3r with geeetech's config for PLA.
What can be the issue ?

Nozzle 0.3mm
Layer height 0.2mm
Extrusion width 0.45mm

Can someone share slicer settings for 0.3mm nozzle ?

how about use this one here:

Thanks Mark it worked out quite well. It is better but slightly smaller.
How to make small adjustments to size ?
Change steps for X/Y or extrusion multiplier ?
Right now I have 80 steps and extrusion multiplier 1.

yes just fine tune the X/Y/Z/E steps so you can improve the precision.