The status output in the shell window tells how many pairs of rigid objects are considered for the collision test and if the displayed configuration contains a collision:
Colliding pair: <collpair> Collision set size: <collset-sz> (<num-pruned> pairs pruned)
The collision checker is always active to tell if the configuration in the graphics window is in collision or not (see output 'Colliding pair: ...'). If there are collisions of more than a single pair of objects, an arbitrary colliding pair is reported in the status output in the shell window. If the minimum workspace clearance delta is set to a value >0, collisions may be reported although there are no real intersections. The output 'Collision set size: ...' tells how many pairs of rigid bodies are actually checked for intersection ('collset-sz'), and how many pairs of objects were not included in the collision set because they cannot possibly collide ('num-pruned').