Default value is 3 slot counts for auto save. You can do it in menu Maximum Auto-Save slot Number. For example, if you entered value 2 in menu Set period between auto-saves and selected Sim Hour in menu Period between auto-save is counted in, Auto Save will be triggered every 2 Sim Hours :)! Default value is: Sim Hour.
Set period between auto-saves - Period between Auto Saves.Enable or disable Auto Save with Enable or Disable Auto-save menu.