Honestly, he's a little surprised she didn't make it anyway. So she's not entirely doing the Force thing. That's good, for his purposes.

"I can't tell how much is your aim and how much you're sensing." The tone is a bit apologetic, that's not exactly the nicest way to go about it but it's a little hard to tell. "Even with a blaster you'll want to use the force. I need to know you can shoot without it, too."

It's the opposite of the problem Luke had, at first. She's good-- instinctive, almost-- with her control, as long as she's focused, but he wants to know she can use her eyes just as well.