There are many options in Rx-Universe to control thickness and thickness tolerances of lenses.
Default Thicknesses
For each job, "default" thicknesses will be determined, based on the power of the lens, the type of frame edge, and the lab's preferences.
...
If the lens requires thickness to be added to satisfy the "Sum of Thickness" condition, this will be printed on the work ticket:
Finished Lenses
When considering finished lenses for blank selection for plus jobs, Rx-Universe will look at each finished lens, and calculate what the final edge thickness will be, for the frame and Rx, using each finished lens. If the lens has an edge thickness within a specified tolerance, then it will be deemed acceptable, otherwise it will be rejected, and blank selection will consider the next possible lens.
...