For those that don't understand baseball, here's a simplified explanation: Catchers will give the pitcher a hand signal like this one to suggest what type of pitch (fastball, curve ball, etc) to throw next. The pitcher has the option to "shake him off" by shaking their head "no," and the catcher will then use a different signal to suggest a different pitch until the two agree on what pitch will be thrown. This is important because the catcher needs to have an idea of where the pitch is going to end up so that the catcher can have their mitt ready in the right spot.

Amber, however, doesn't want to communicate with a "no" because she's afraid it will blow her disguise, so she ostensibly accepts the fastball suggestion and continues with her wind-up, about to throw a curve ball in actuality unbeknownst to the catcher.

Hopefully that makes sense! Yaay baseball ^_^