I recently brought this minimum size tolerance subject up on the Australian forum.
Stating a required stone size of 10mm +/-0.1mm is easy to understand. The stone has to be between 9.9mm and 10.1mm or it will be disqualified.
Stating a minimum stone size of 10mm +/-0.1mm to me doesn’t make sense. You can cut the stone any size you like as long as it’s not smaller than 9.9mm.
To me it would be much simpler to understand if there was no tolerance stated and the minimum size is 10.0mm. It’s down to the cutter to know how accurate his measuring equipment is, which he needs to know anyway when cutting a stipulated size stone to within 0.1mm.
The judges can apply a 0.1mm tolerance when measuring the minimum size just the same as when measuring a stipulated size.