The Element Numbers option in the Display Options dialog, will display the number of each finite element, as used in the Phase2 input and output data files.
When Element Numbers are displayed, they will overlap in dense regions of the mesh. This is normal, use the Zoom Window option to zoom in and make numbers readable.
You may also want to toggle on the display of Elements, when viewing Element Numbers, if you are performing a detailed inspection / troubleshooting of the mesh.