Your post is unclear.
If you designate a group or frequency as Priority, then when you enable Priority mode, the scanner will "pause" every two seconds to quickly check for activity in the designated frequencies. It will stop on any it detects, then continue scanning.
Priority Plus mode will only scan your priority frequencies, none other.
While your scanner may be different, I prefer to use a separate designated system with all my "priority" frequencies. That way my scanner doesn't keep chopping up the audio on a freq I am listening to to check priority freqs. It's also faster to simply disable all other systems using quick keys and only turn on quick key 1.