ElephantDrive backups are incremental. When a file is backed up, ElephantDrive will keep its most recent copy (current version). If the file is modified, ElephantDrive will detect that the file has changed, then upload the modified file and keep the previous version of the file.
Let's say you have a text document (file) backed up to ElephantDrive and you decided to make some edits to the text document (i.e. adding more paragraphs, changed formatting, etc.). Once you save the edits, ElephantDrive will upload the modified file as the most recent copy of the file, but it will also keep the previous copy of this file as a version in your ElephantDrive account.
How many versions are kept and for how long can be changed by modifying versioning rules. To change how long to retain versions, please edit your backup settings. (Click here to learn how to modifying your backup settings.)