This example shows how to "debug" a Condor job — and illustrates how class ads work:

condor_q -better-analyze <JOBID>
.
.
The Requirements expression for your job is:

( target.Arch == "X86_64" ) && ( target.OpSys == "LINUX" ) &&
( target.Disk >= DiskUsage ) && 
( ( target.Memory * 1024 ) >= ImageSize ) &&
( TARGET.FileSystemDomain == MY.FileSystemDomain )

    Condition                     Machines Matched    Suggestion
    ---------                     ----------------    ----------
1   ( ( 1024 * target.Memory ) >= 2570000 )0              REMOVE
2   ( target.Arch == "X86_64" )       154                   
3   ( target.OpSys == "LINUX" )       154                   
4   ( target.Disk >= 10000 )          154                   
5   ( TARGET.FileSystemDomain == "..." )
                                      154                   

Thanks to UWCL. . .