You cannot change PRE / POST time, these are predefined.
Please refer to the below table,
RESOLUTION / FPS | EVENT MODE | DUAL MODE |
1080P / 30fps | 15sec / 15sec | N/A |
1080P / 15fps | 10sec / 10sec | |
1080P / 10fps | 10sec / 10sec | |
1080P / 5fps or 1fps | 15sec / 15sec | |
720P | 15sec / 15sec |