This article explains how to set individual storage quotas for ownCloud users.
Log in to the web interface for your Datto appliance.
Click on the Configure link, and then click Device Settings.
You will see the Global Device Settings page, as shown in Figure 1.
Figure 1 - ownCloud
Copy the ownCloud admin password, and then click the ownCloud here link. Use the admin password to log in.
Once you're logged in as admin, click the admin menu in the upper right. Then click Users.
Figure 2 - Admin Menu
From there, you can adjust storage quotas on a per-user basis, as shown in Figure 3.
Figure 3 - Quota Column