Right you are.
For all you developers out there, here is the lesson: some php implementations are 32-bit and upon attempting to parse an integer larger than that, they return (pow(2,31)-1), since they are signed integers.
Thus, you might have noticed that the maximum order on the book was 21.47483647 before others came across the socket. This is equivalent to (pow(2,31)-1) / 1e8.
Fortunately, this code fix was server-side, so the client code still functions properly.