When you export your contacts' statistics and settings, it will only copy Contacts key of an account in the registry. However, there is a ContactWatchTime value which is under Preferences key but directly related to contacts, and unrelated to Preferences. And without this value, when you import that statistics to a new computer for example, the contact list clean up window doesn't show the same information it used to show on your old pc, on the new pc. To make it appear the same, you have to export&import your General Preferences too.

The ContactWatchTime value should be under the Contacts key imho like in the ss. It is more meaningful also.