Lenovo LT2223dwC User Manual page 12

The 2 USB ports on the side are the downstream ports dedicate to USB 3.0 upstream port
(on the bottom of monitor), they are compliance with USB 3.0 standard.
The top one is compliance USB battery charge standard version 1.2, that can charge
portable device, max to 2A current.
The 2 USB 3.0 ports are the downstream ports connect to USB type keypad ,
plug in the USB type keypad to this ports or plug in the USB type Mouse to this port.
1-8 LT2223dwC Flat Panel Monitor Users Guide