The AFS command fs is used to examine attributes of the file system. Full documentation can be found on the fs command via the manpage that has references to all of the fs subcommands.
The fs listquota command shows your current quota and current utilization. In the following example, the user has consumed 9% of their home directory quota and none of their web and backup volume quota. The quota is tracked in 1KB increments. The last column is not your quota, rather it is the total available space on the disk volume holding the given afs volume.
$ fs listquota ~/ ~/public_html ~/Backup Volume Name Quota Used %Used Partition U.username 1000000 86198 9% 2% U.username.web 10000000 3 0% 2% U.username.arch 2000000 4 0% 2%