First, they are not static or manual routes being defined, they are just IP assignments.
The difference is;
DHCP = IP given out by the router from it's configured pool of IP's
Manual = IP given out by the router (via DHCP) where you have created a MAC<>IP bind in the DHCP Server settings page
Static = IP the device has been given in the device's own config, so the router has not given it any IP via DHCP (or at least doesn't remember doing so recently - see below)
The confusion is Static can also appear in one of the following 2 scenarios;
1. The router has been rebooted and the device has not yet renewed it's DHCP lease. Or the device has had a temporary loss of connectivity and not renewed its DHCP lease yet (this would be a loss the router noticed but the device didn't, rare, but happens). So from the routers point of view, a device is on the network with an IP it doesn't remember giving it (or has no current DHCP lease)
2. When first opening the Client List page, a bug sometimes causes it to temporarily (for maybe 5 seconds) show ANY device which has previously connected to the router, even if it is not connected right now. As these devices have expired DHCP leases from the routers point of view they appear as 'ghost' static IP's.