When uploading and processing many thousands of photos for an event, it is necessary to keep track of what you've uploaded and how many photos are online. There are a couple of tools to become familiar with:
This tool shows the individual upload sessions and associated photos with those sessions. Just click on the ID number for the session to see a list of the photos uploaded. That list will show the original file name and the Backprint file name. You can use this to see where an interrupted upload left off and where you need to start uploading again.
The photo manager allows you to hide/delete, categorize, update photo tags and place wholesale photo orders. It also shows two photo counts. The total photo count is how many photos were uploaded to the event. The Active Photo count shows how many photos are displaying online. Active photos do not include an photos that have been hidden or deleted. Hidden/deleted photos are shown in the photo manager, but greyed out.