The following comes from Mark's Easier to Read Scanner Manuals:
P25 Adjust Mode this is a hidden setting accessible only by turning off the radio and pressing Hold when you turn the scanner back on. (For now, this is just a test setting and can be ignored). This mode sets the algorithm for P25 decode. Leave it at 3. Anything higher than 3 will just act like 3. Anything lower will have the reduced performance of previous firmware versions of the 396T.Scroll to 'P25 Adjust Mode' and press E/yes.
Enter 3-15 and press E/yes to save and exit. P25 Adjust Level this is a hidden setting accessible only by turning off the radio and pressing Hold when you turn the scanner back on. Sets the RSSI value below which the scanner will not attempt to make P25 fine tune adjustments. If the signal is too low, RX reliability is not high enough to make P25 adjustments correctly. The default value is 50.Scroll to 'P25 Adjust Level' and press E/yes.
Enter 1-200 and press E/yes to save and exit.
Which combination of Adjust Mode and Adjust Level that works best on the digital system you wish to receive is a matter of trial and error. One size does not fit all.