Number of lines that match selected search pattern is displayed under search pattern text box in glogg and to the right of that text box in klogg.
Counting number of lines that matches quicksearch (the panel in the buttom part of main window) is hard right now. Quicksearch is done incrementally. It shows matches only for the part of file that is currently visible. And only if there is no visible match then search is done for some next occurrence. Counting all matches would require full pass through the file. In glogg that would cause UI to hang as quicksearch is done in main UI thread. In klogg quicksearch runs in background and it might be possible to modify it to find visible matches and continue to count all occurrences, but for now I don't see good UI for indicating this. Feel free to create a feature request on Github for discussion.