From: DeskNow Knowledge Base
http://www.desknow.com/kb/

How do disk quotas work in DeskNow?
http://www.desknow.com/kb/idx/16/066/article/
DeskNow has three levels of disk quota. You can assign a disk quota to a user, to a community of users, and to a domain. The disk quota of a community is simply the sum of the disk quota of its users. The same applies to a domain.

DeskNow has a soft-quota/hard-quota mechanism. When you set the disk quota of a user to 100 Mb (for example) , DeskNow will show the disk usage as 100% when the user disk usage reaches 100 Mb (this is the soft quota).

To leave a bit of room to the user, Desknow will actually allow the user to have up to 120% of the quota (120 Mb in the example - this is the hard quota), before blocking any more mail to be received, files to be uploaded, and so on. This approach ensures that a user has enough time to clean up his/her mailbox before the system starts rejecting mail for the account.

The same concepts of soft and hard disk quota apply to communities and domains.