You can change how long file history is saved both for your reseller account, and your customer's account.

In order to change the file history for a company, first, the max days for your reseller must be lowered to that amount, because a company/sub-reseller cannot have lower history settings as the main reseller.

Then, you need to change it for the company as well.

To get to these settings, login to your reseller site, and click on the History tab.

Max days is the days a versions is saved.

If the setting is set for e.g. 60 days, versions of files will be saved for 60 days before they get deleted on the server.  

Max versions is how many versions of a file you keep.

A file can be saved multiple times during a day, and every version takes disk storage.

These settings allows you to clean old versions to clear the data usage by setting them lower. 
(We do not recommend going below 30 days / 30 versions, in case you need to restore your data).

The cleanup service that cleans older versions of files runs at 2:00 every morning, and can clear up to 5000 entries, so it might take a day to see the change occur in your storage usage statistics.