Keyestudio Micro:bit Mini Smart Robot Car V2 Instructions Manual page 76

When the front number are set to 0, motor turns forward; set to 100, motor turns reverse.
In the code, LED2 and LED4 are setting the motor's speed, in the range of 0-100.
The greater the value, the faster the speed.
Below table is the running status settings of Micro:bit robot:
50