Clutch Wear Calculation - Am I Calculating Right??

Hypothesis would depend on how you determine the wear limit.
Is it the remaining friction material above the rivet heads (usual way) or the loss of friction material from the new thickness?

Do the grooves represent the wear limit? I.e. no visible grooves....clutch fully worn.

 

Of course, it's depend of wear limit.
Ferrari say 0,8mm by cluch, and Maserati say - in "Advanced-Electronics-1-Engine-and-Powertrain" file - that wearing should be calculated with 5,6mm.
These 2 values are consistent with each other.

May be it should be calculate with another value for some Ferrari/Maserati cars, but I have no data about that.

Concerning grooves, if Ferrari say max wear is 0,8mm, grooves must are deaper than this value (for evacuate dust).