When you save changes to the project, Revit does the following:
The local backup file provides protection in case the network save fails. Revit saves up to 3 local backup files. It purges older backup files.
The local backup file uses the same name as the project file, with a GMT (Greenwich Mean Time) date and time stamp appended to it. For example, when you save project.rvt, Revit saves a local copy to the Journal folder, using the file name format project_YYYYMMDD-hhmmss-mmm.rvt.