This condition evaluates true for any non-system database other than distribution and ReportServerTempdb whose last differential backup is more than 48 hours old.
Edit query to ignore all user databases not included in differential backup jobs
Ignores all system databases, distribution, and ReportServerTempDB databases.
Ignores Read Only databases
Ignores databases in a standby state
Ignores databases identified as a database snapshot
Default threshold is 48 hours, please change to meet your own SLA's
Set to check every 8 hours.