The reason you don't see a difference between setting 0.1mil and 1.0 mil tolerance is because the "line segments" you are converting (in your design files) probably already form a perfect arc. The tolerance setting is used when you have "line segments" that do not form a perfect arc, and perhaps have one or more points that are X distance off the arc --- typically this is due to floating value rounding. By increasing the Tolerance, ACE 3000 will accept those points "off the arc" by the tolerance setting you set.
Thanks again, and please let me know if you have any other questions.
Best regards,
Simon
Numerical Support Team
http://screencast.com/t/V8x3bnZ8Pm7