This is a read-only counter, in pages, tracking the number of fax-related image pages received or transmitted through this peer during the current call leg. An admin monitors this on active fax calls to track fax transmission progress or to confirm that fax pages are actually being exchanged rather than the call stalling. For example, a fax call that shows this counter stuck at zero for an extended period would suggest the fax negotiation completed but no actual page data is flowing.