The Simple Edit Counter (or Simpler Counter) is a quick and fast edit counter providing only basic information such as the user ID, user groups, and the live and deleted edit counts.
Just as with the main Edit Counter, the Simple Counter makes real-time queries to the database. For this reason, your system edit count as shown in your preferences may be different. The system edit count is a running tally of all edits made by the user (even if they were later deleted or suppressed). In addition, the definition of what constitutes an edit towards your system edit count has changed over time. For instance, page moves have only been counted as edits since June 2017.
For this reason, the system edit count can be considered approximate, while XTools is more exact as it does live counts on the database.
However, if the requested user has made an exceptionally high number of edits, only the system edit count is shown for performance reasons.