The number of transferred modules' Items and available for transfer items can be different, because not the all profiles can be transferred and some mandatory fields required for UNA modules may not exist in Dolphin modules records. For example, your UNA site may already has admin profile and thus admin from the Dolphin will not be transferred and all his media files, forums and etc... also. So, you need to direct your attention on final green message which appears when transfer is complete. It contains the all transferred records.
If you have many items in modules, it would be better to transfer them one by one and don't select the bulk of modules. Also if you have any database management tool ( phpmyadmin for example), you may open it and check if the number of records for selected module is increasing when you start the transfer. It allows to understand if the transfer is still active and continuing.