Where to modify feed status to change number of created and updated nodes
in feeds.pages.inc, function feeds_source_status() the status information is shown for the importer, including the number of imported items. The number of items is calculated in FeedsProcessor::itemCount() in plugins/FeedsProcessor.inc.

The message of how many entities were created and updated happens in FeedsProcessor::process(). FeedsSource::$state keeps track of these numbers. The case where these numbers might not be accurate is if the same entity is updated multiple times in a single import. Usually, this is caused by a configuration error: the target that is configured as unique appearantly isn't unique in the source.