The Quota Editor allows you to alter how much disk space an account is allowed.
Note: If all of your account's quota amounts are listed as zero, which you know is incorrect, then your quota.user file is probably corrupt. Run the script at /scripts/fixquotas.
To alter an account's disk space quota:
Click on the Quota Modification link in the Account Functions menu.
Enter the new quota amount next to the required account in the Quota field and click on the Change button.
Repeat the procedure for multiple accounts.