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