Why does sync.blue® say that more contacts are synchronized than are in the source?

In specific situations, according to sync.blue® connections, more contacts may be displayed as "synchronized" than are present in the source. The most likely reason is that contacts in the source were manually deleted after creating the sync.blue® connection. sync.blue® retains references (not contact data) in a kind of "cache" and remembers the mapping to the target contact. Deleting and recreating an identical connection should then display the currently updated (lower) number of contacts.