The NVR manuals are typically not consumer-friendly. English is poor ("Chin-glesh?).
One manual covers many, many models.
Terms are less than ideal. ("delay" can mean debounce, duration, and yes, delay).
When learning this stuff, I sought out better information, so I didn't need to rely solely on the Dahua manual. I never found anything really useful.
Searching here was more productive, even considering the hit-or-miss searches to find others who had asked a question like mine...
Printing section of the manual, then highlighting and scribbling notes ended up being my MO....
Good luck,
Fastb