There's an awkward pause before Strange answers, "Enough until they have enough data."

And as much as he really doesn't want to talk about this and he wants to keep Yuya from worrying about him...Strange is slowly coming to terms with the fact that he can't do that. His situation is just fucked enough that it's really no use trying to pretend that he has everything under control (just most of it.)

"They want to see if my body can adapt to growing more samples of the Silver Mirror. So, they started with my arms." Awkward pause before Strange clarifies. "The, erm, inside of my arms."