CCS has two databases. Device and Agent. Device doesn't care who is on the phone, or what they are doing. Calls by Extension is just such a report. The filter is your greatest friend or worst enemy. Especially because of the two database system. Calls by Extension will generally show a higher number than the Calls by Agent. Calls by Agent shows activity while they were logged into a hunt group. If they log out, any activity on the phone will not show up in this report. The Calls by Agent should use a filter with the desired hunt group listed in the ACD Hunt Group tab of the filter. The Calls by Extension should list the extensions you want. Since you're talking about DID calls, I would suggest checking the external calls only box on the report options. You may end up having to export everything to an Excel file, and extract anything the went through the hunt group.