Well, that's it, zero.
But, it's always polite to express one's appreciation to one's Training Mistress. I love to crush male balls. However, I am not allowed to touch you myself. So, show your appreciation for me by squeezing your balls for at least 30 seconds, though a full minute would be really nice. The way I'd like to squeeze them.
Once you've finished, stroke to the edge, pack up your little ditty bag, and crawl back to Lady Christine.