When records are exported to a file, numbers are attached after User/Group/Department values
If you see numbers at the end of the field values (such as User selection, Department selection, and Group selection) in the exported file, it means that the corresponding users, departments, or groups have been deleted from your environment.
In the value for a deleted user/group/department, the time stamp of the delete operation will be added in UTC (Coordinated Universal Time) format. For example, if a user was deleted on "April 6, 2021, 15:15:36", it will be exported to the file as "login name: [210406061536]".
The same applies to when you export values for the Created by and Updated by fields to a file.