The quota is the size limit of a tubIT account the correspondent AFS directory. 

tubIT provides:

students: 1 GB

employees: 5 GB

departments: 250 GB on application

Step 1: Rightclick the directory you want to check and select

"AFS" -> "Volume/Partition" -> "Properties"

Step 2: This window shows the maximum size (quota) and the used storage.

You can check the used and maximum storage in the bottom left menu bar of the WebAFS interface.

Step 1: Open a terminal resp. start your SSH client and log in with the following command:

local:~ ssh tubit-username@sshgate.tu-berlin.de
Passwort: <tubIT-password>

Upon successful login you will see something like:

Last login: Thu Jun  7 13:43:41 2012 from dhcp-2-219.zrz.

Sun Microsystems Inc.   SunOS 5.10      Generic January 2005
tubit-username@sshgate:~$

Step 2: Command to see the used/available AFS storage:

tubit-username@sshgate:~$ fs lq .