Waitresource format explanation in deadlock xml
It's the Lock Partition


  For large computer systems, locks on frequently referenced objects can
  become a performance bottleneck as acquiring and releasing locks place
  contention on internal locking resources. Lock partitioning enhances
  locking performance by splitting a single lock resource into multiple
  lock resources. This feature is only available for systems with 16 or
  more CPUs, and is automatically enabled and cannot be disabled. Only
  object locks can be partitioned.


You can see this by comparing the deadlock message in the errorlog with the deadlock xml in the system_health XEvents session, which you can query like this:

SELECT 
    CONVERT(xml, event_data).query('/event/data/value/child::*') AS DeadlockReport,
    timestamp_utc, datediff(s,timestamp_utc,GETUTCDATE()) sec_ago
FROM sys.fn_xe_file_target_read_file(
        cast(SERVERPROPERTY('ErrorLogFileName') as varchar(max)) + 
        '\..\system_health*.xel', NULL, NULL, NULL)
WHERE OBJECT_NAME like 'xml_deadlock_report';


From the errorlog:

 Message OBJECT: 2:1013578649:15        CleanCnt:2 Mode:IS Flags: 0x1


from the deadlock xml:

 &lt;objectlock lockPartition="15" objid="1013578649"