Jetracer throttle front and back problems

I’m having trouble making jet racers using Jetson Nano.
In basic motion, the throttle is adjusted to a value between -1 and 1.
In my case, if I enter a negative value, the jetracer go forward and positive values ​​work the opposite way.

At first, I thought it would be fine to adjust the reverse on the transmitter.
But it only works when controlled by the transmitter, It was not related to basic motion.

how can i solve this problem?

Can I simply put a negative sign before the throttle value x?