"Yes, ma'am, I understand." Dean doesn't pull at the knots to test them; he'll take her word for it. For now, his hands stay clasped, giving himself something to hold onto to make sure he doesn't pull by accident.

There's a thrill in being bound tightly enough that he could pull against them without breaking free, but for a first encounter this is better. Safer. After this encounter, who knows? Maybe he'll ask for those tighter knots.