There's a small little pause before Strange starts very tentatively talking again.

"I realize asking this is an imposition. However, if you make it to Delta before I do, can you try and get a look at my lab records? They withdrew something silvery from my brain that didn't look at all like my interior mirrors. I'd like to know what it is."

He knew the Silver Mirror had changed him. He just didn't know to what extent: the silvery whatever is equal parts interesting and worrisome.

Also surpriiiise, Strange has inside mirrors now. Does Rita know that? He's not sure if she knows that.