Lucky you! My drop down list will not populate at all! (see this thread) I even MANUALLY inserted the MailChimp listID into the settings table, and still it doesn't appear in the drop-down...
Hi. 10 it's a default number of items returned by MailChimp pagination system. We have fixed this bug and now you can see all the lists on configuration page (after re-uploading the plugin). The changes can be found here.
Unfortunately, at the moment we are not able to analyze the synchronization errors in the plugin, we can only state that something has gone wrong. Errors for example can mean that subscribers already in the list and you are trying to add it again, or maybe something else. Also you can try check the errors in the API calls history at your MailChimp account -> Profile -> Extras -> API keys.