If you want to count number of edit by a user you should group by user id like :
select count(occurence) from tableName group by userId
This would fetch from the table for all user for entire time range.
For specific user or for a specific time period then you can mention in where clause.
If you will group by timestamp then you will get all the edits that had been made at that particular time.
If you will group by timestamp + user then it will give all the edits that have been made at that time per user wise.