To set the options for the autosaved copies of your site, go to Tools > Current Site and select the Backups tab:
Naming convention. Choose a preferred naming convention for site autosaves. Site autosaves will be named using either the site name and version number or the site name and date the version was created, depending on which option you choose.
Backup location. Choose a location on your local hard disk to store autosaves of site files.
Total size of autosaves. Enter a maximum value (in megabytes) of hard disk space to be allocated for site autosaves. You will be prompted to remove previous autosaves when you exceed this value.
Total number of autosaves. Specify a maximum number of autosaves that can be stored on the local hard disk. You will be prompted to delete previous autosaves when you have exceeded the maximum number of autosaves allowed.