Other mistake: When Rex shakes the table causing the baby monitor to fall, the batteries fall out and we see the open battery compartment with markings for positive (+) and negative (-), and space for two AA batteries. Woody jumps off the bed and places the two batteries inside the compartment, but before he closes the compartment note the position of the battery closest to the top of the monitor. The positive side is actually where the negative side should be so the monitor should not work, but the monitor turns on just in time to hear the soldier's warning. (00:13:15)
Answer: Baby face taps RR TOYS COME OUT. Telling the other toys to come out from hiding. Pixar stated this in their Toy Story character overview.
But why "RR"?
"RR" is shorthand for "Message Received." Babyface is telling Woody that he understands Woody's problem and then taps out to the other toys to come out.