{subsection: How to preempt (evict) a job that uses too much disk space}
 
-The following configuration settings should be put in the config file of the execute machines (or the whole pool).
+The following configuration settings should be put in the config file of the execute machines (or the whole pool).  The reason a number must be inserted for MAX_DISK_USAGE_KB instead of using the Disk attribute of the machine {quote: ClassAd} is that the Disk attribute measures the amount of free space on the disk, not the amount of space promised to the job.
 
 {code}
-DISK_EXCEEDED = DiskUsage > Disk
+MAX_DISK_USAGE_KB = insert_number_here!
+DISK_EXCEEDED = DiskUsage > $(MAX_DISK_USAGE_KB)
 
 PREEMPT = ($(PREEMPT)) || ($(DISK_EXCEEDED))