What SyncNow keeps is the previous content of files its tools overwrite, a record of who changed which files through it, and, for projects whose source authority is SyncNow, the history of the canonical repository.
Previous versions are kept on the SyncNow server, never on your site: up to 20 per file, none over 2 MB, no binary or media files, never the content of files that look like configuration, and older copies can be removed by a scheduled cleanup. An agent can only add to the canonical repository's history, never rewrite it, and uploads, databases and other runtime data are not in it.
SyncNow's own data, including project repositories and project memory, is copied to an encrypted backup outside its hosting, and each copy is downloaded again and checked before it counts. Database changes made by an agent with db_exec are not versioned by SyncNow, so back up a database before risky work.