A-Axis Calibration - Stepcraft 420

Hi everyone. I was looking for some tutorial or a topic in this forum, but i didnt find. So, I'm trying to make a 3d printing, using Stepcraft 420, UCCNC and
stepcraft Repetier-Host with Slic3r.
In the UCCNC, calibration on the A-AXIS, what value do I need to declare in the "Steps per Unit" field? I know that in X,Y and Z Axis the value is 133.3,
but in the A-Axis (extrusion)?