Currently, the scene outliner shows the total number of actors in the scene in the lower-left corner (“1249 actors”). If I select multiple actors, I expect it should also tell me how many I have selected (“1239 actors 37 selected”). Right now, there doesn’t seem to be any easy way to determine that, and I end up having to count them manually.
Alternatively, you can cut your eyes up at the Details panel.
No problem! Glad I could help. Actually, I’m just glad that’s what you were actually looking for.