Monitoring transac replication

Hi,

I have 2 servers setup in a bi-directional transactional replication. At the moment I monitor these in an external tools by using:

* sp_replmonitorsubscriptionpendingcmds => gives me an aggregate of all the pending commands

* And the following that gives me the detail

 select article, UndelivCmdsInDistDB
from distribution.dbo.MSdistribution_status  X (nolock)
 join distribution.dbo.MSdistribution_agents Y (nolock) on   Y.id=X.Agent_id
 join distribution.dbo.MSarticles Z (nolock) on Z.article_id=X.article_id
 where UndelivCmdsInDistDB>0 and z.publisher_db = DB_NAME()
 order by 2 desc, 1

For one of the server the value pretty much matches. However for the other servers, the 'detailed' view has an order of magnitude higher of a 100 compared to the aggregate. The aggregate is also extremely flat compared to the details view.

What could explain the delta between the detailed view and the aggregate ?

Thanks