Centova Cast's disk quota includes all files and subdirectories in the account's directory under vhosts/ -- this includes logs, configuration files, and so-on, just like a traditional UNIX quota.

So for example, if the media for the account is consuming 500MB, and 75MB of logs exist, then the total disk space usage for the account will be 575MB.

Centova Cast rotates the log files automatically every 12 hours, retaining a total of about 48 hours worth of log data at any given time.  If the log file sizes are impacting your users' ability to store media (and/or resulting in undesired suspensions), you may wish to increase your quotas by the average size of your users' log directories to compensate.