Those appear to be power connectors for RAID cards. If you put a storage controller on that riser that requires backup power, those ports on the riser are where you would plug them in.
Here's a section of the user manual that shows how you would use this. It refers to a section called "riser board components" which looks like the page you snipped that graphic from. (Hint - in the future, include links to resources like that.)
Cable routing: Smart Array P824i-P Controller
Backup power cable
A smart storage battery is required with this controller. Your riser
might look different from the one shown. To locate a backup power
connector, see "Riser board components".