Please refer to the detail below:

1 light flash for 5 seconds: DPI is set to 800.

2 lights flash for 5 seconds: DPI is set to 1200.

3 lights flash for 5 seconds: DPI is set to 1600.

4 lights flash for 5 seconds: DPI is set to 2000.

4 lights flash for 2 seconds: power is turned [ON].

4 lights flash all together for 5 seconds: run out of battery.