"Cylinder 5 misfire detected" is the count of firings in cylinder 5 that did not produce the power they should have, on an engine that has a fifth cylinder to count. The number is the engine computer's own numbering, and the code differs from P0300 only in being attributed to this one cylinder.
This is a standard code. It means the same thing on every make of vehicle.
The Dashboard draws one Misfire cyl card per cylinder the engine actually reports, so a Misfire cyl 5 card appears only on an engine that has one. The Full scan's per-cylinder table shows its count for the last ten drives and for this drive next to the others.
The Dashboard's Misfire count cards show one counter per cylinder once the engine is running, next to the Engine speed and Ignition timing traces. The Full scan's On-board self-tests give each cylinder's misfire count for the last ten drives and this drive with its share of the total, and a recorded drive works out a misfire rate over that recording for the Analysis screen and the printed report. The Inspection screen shows whether the Misfire detection monitor is done or still running.