Calls answered/presented by RG agents are taken from Skype/Lync monitoring database from CDRs(LCSCdr db).
In this case, in the legs we can see sip address or extension number, also the RG that they belong as 3rd party.
That’s the number of extensions assigned to any particular employee which had activity (placed/received calls) during the reported date frame. Any user can have multiple extensions assigned and that column will report on that.
Yes, there are several ways to do that. For example you can report on participants calling from PSTN which is direction OUT so can report on that as well and you can exclude callers from your own company like yourcompany.com