Jyn only waits with raised, slightly impatient eyebrows as he decides, the natural downturn of her mouth making her look like she's frowning. When he makes his decision, she deftly plucks up two cupcakes and moves them in front of him with a no less serious face.

"You chose correctly."

Rationally, a whole cupcake with half the frosting would be better because you can just spread the frosting, but Jyn is not about that diet sugar life, she is here for the frosting and since Percy joined her in that life she is choosing to reward him.

Plus he looks school aged and she doesn't think he should be financially supporting his own education.