The status bar shows (along others) the number of counted lines.

Sometimes it counts one line to much . see images. What's the background?

The status bar shows the number of line terminators found in file plus one, i.e. the number of carriage return + line-feed pairs in a text file using DOS/Windows line terminators incremented by one. A string at end of file with no line termination is technically no line. But in a text editor this string at end of file with no line termination is displayed nevertheless on a line. I suppose plus one is used to get displayed the same line number in status bar as in line number area on no line termination at end of file. It would be more accurate not incrementing the number of found line terminators by one on file ends with a line termination in my opinion.

But sometimes it does not "add plus 1" - see above, see here. But that's not that important; more a strange thing. Maybe @idm will take a look.