The number of rolling elements has to be specified. A minimum number is three; the maximum number depends on the bearing pitch diameter. A warning is shown if the rolling elements overlap, the distance between rolling elements is available in the results overview and report.
For cross roller bearings, this is the number of rollers for one row.
Using the -button the number of rolling elements can be calculated automatically based on a maximum fill angle and a minimum distance between the rolling elements. For deep groove ball bearing the fill angle would be 180-200°, the minimum distance can be based on requirements for the cage.
This option is mainly thought to allow the variation of the rolling element diameter in the parameter variation with an automatic setting of the number of rolling elements.