The ledge for the clutch must be 21.0mm above the disc surface when they're done.
When you are there, tell them to grind the disc surface, then grind the ledge down to 21.0. Most shops wrongly think that if they take .25mm off the disc surface, all they need to do is take .25mm off the ledge. This is wrong because it preserves the wear from the flywheel's previous life. Clutch slippage is guaranteed if they do that.
