[200q20v] Rear Caliper Specs? Bentley is confusing me..

[Calliope]

The Bentley says the rear disk should be between 10 and 8 mm thick. Is
that the total thickness of the disk, or the thickness of just one of
the faces?

My disk is about 20mm in total thickness, which makes no sense compared
to the specs, but if I measure the individual faces (seperated by the
ventilation gap), they are each about 6.5mm thick.

Time for new disks, or what...?

Thanks

Tom F.
'91 200q20v Avant...back in the garage.