I was just struggling with auto relief for a sheet metal part.  I creating an edge flange and the auto relief was very small. 

You can find the settings for it by right clicking (See attached picture because I dont know the name). 

Selecting Edit feature and then changing the value in the Auto-Relief section.

This value is actually a ratio of the thickness of your material, not the size of the auto relief.  With 1.0 being the same thickness as the thickness of your material.  For any CNC punched part the bend relief should always at minimum be the same width as the thickness of the material (smaller reliefs will significantly decrease tool life).  If the part is going to be laser cut the relief must be smaller.