Each line has missed call badging. You can view the number of missed calls per line on the phone screen. The maximum missed call badge is 99. When you view either the All calls or Missed calls list on the phone screen for a particular line, the missed call badge for the selected line gets cleared.
The missed call badge and the actual number of missed calls may be different due to a display limit of 180 calls for the Recents list. This limit consists of outgoing calls, missed calls, and incoming calls. Also, there can be some old missed calls that get added to the count for the missed call badge. This can get overwritten in the Recents list.