Push notifications require persistent TCP connection with the server.
On mobile devices, TCP connection is often broken when a device is sleeping and the connection is inactive, usually after 10-15 minutes of inactivity.
Therefore, Headwind MDM sends "Keep-Alive" packets to keep the TCP connection active. "Keep-Alive time" is the time interval between such packets.
5 minutes seems to be an optimal setting. I don't recommend setting a larger value. You can set a smaller value, but this will consume more traffic and battery.