Is total server quota a firm quota?

Is the total server quota a hard quote? IE: if the quota is 1024 mb, is that space allocated and taken from other usage on the disk or is it just a file size limit that can't be gone over? I ask because giving 1024 mb as standard could use up a disc pretty quick if it is unavailable, especially if the site only needs 50 mb.

Also what is the difference between total server quota and server administrators quota? I'm assuming they should be the same.

Thanks.

Mike Murphy