Uniden made the number tags so that you could stop scan and then enter a number to very quickly select a system and a single conventional frequency to monitor. But not so with sites. The number tags are then for systems and TG's.
While the scanner are scanning and have not been manually stopped the quick keys are used to enable and disable system and sites from the scanning process. As Eng74 mention you have to toggle all other sites to Off. First push the system button while the scanning cycle are in the desired system to only scan that system, then push the quick key number combination for the system and the sites to turn them on or off.
It's probably easier to push System to hold on to the system and then push the Function button and the Department button will change to a Site button. Push that Site button to hold on to a site. Wait until the Fn symbol disappears from the display, after 2 seconds, and push Function again and the Site button and then turn the dial to go to the actual site you would like to monitor.
When you push the System button and you happen to be holding on to the wrong system, wait 2 second for the HOLD indicator to turn on and push the System button again and turn the dial to go to the correct system. As long as the system name are highlighted on the display you can use the dial to step thru the systems. After 2 seconds from the last dial use it will turn back to normal again.
/Ubbe