"Source Items" and "Target Items" QMM Statistics counters are different from "Total Items" report (4217397)

When looking at Statistics information for the mail or calendar collection the amount of items reported may be different from what is displayed by Microsoft Exchange Administrative tools such as Exchange System Manager (ESM) or Exchange Management Console (EMC).

QMM agents enumerate all folders under Top of Information Store and read PR_CONTENT_COUNTMAPI property on each of them.  The resultant sum of all the counters will be reported by Statistics Portal for the mail items, excluding the counter for the Calendar folder which is reported separately on the Statistics page for the corresponding Calendar synchronization collection.  This may not correspond to the information displayed by Microsoft Exchange Administrative tools such as ESM or EMC - please see the detailed explanation below.

While QMM reports actual mail (including Tasks and Contacts) or Calendar items within the source or target mailbox, the Microsoft Exchange Total Items count may far exceed it because of the below explanation from Microsoft.

Determining the True Amount of Space in an Exchange Database - http://technet.microsoft.com/en-us/library/aa996139(EXCHG.65).aspx

Within a mailbox, many hidden items exist.  Some of these items include third-party hidden folders, rules, and items used to support the functionality included with an Exchange mailbox.  These hidden items are sometimes referred to as NON_IPM_DATA.  Exchange System Manager considers all related mailbox data, including NON_IPM_DATA when calculating the size of a mailbox.

Also QMM Agents may not enumerate some hidden mailbox folders that reside outside of the Top of Information Store such as BlackBerry that keeps its data under the root.

Basically the formula is:

ESM (Total Items) = QMM Stat (Mail) + QMM Stat (Calendar) + MS Exchange InternalItems + MS Exchange Hidden Folders (including 3rd party)

Please also see the following Quest KB article SOL14954 - When synchronizing a mailbox there is a discrepancy in the amount of items reported between the source and the target. - https://support.quest.com/SUPPORT/index?page=solution&id=SOL14954