When using groups in the event sheet, gdevelop does not give the correct line number of events after a group. As a result the total number of lines in the event sheet is not counted properly. Events put inside a group should not be counted as 1 event line.
This is a “feature” in the way that events are not a flat list, but a “tree” (that’s the technical term) and so events only have an index relative to their parent.
That’s the same for subevents 
Can be a pain at first look, but it is easier to tell people to look at “Events 4 > 8” of the group “Player events” instead of “Event 418, errrr sorry 419, errrr ooops I just added another event”.
Ah I see, sorry for the confusion.
I guess the only downside is that it is kind of hard to figure out the total number of events, when using groups
Maybe what you really want is some counter e.g. in status bar that says how many events there are in the scene?
As a rule of thumb, if you feel there are too much events => Use external events to structure your events sheet into big logical blocks <=