Upload vs Import (Staged Upload)
Picturepark uses a staged upload process. Files are first uploaded (available to Picturepark (Storage)) and then imported (Picturepark starts Rendering & Data Extraction). The process stage is visible in the notification where you see 1. xx files uploaded, then 2. xxx files imported.
In most scenarios, you will not care about the difference. Still, in the case of a lost internet connection during upload, you will find your "broken" uploads in the notification area. You see uploaded and imported files there, so you can quickly identify the ones, you must upload again. Without transfers, you would need to check for each file if it is in Picturepark or not.
Picturepark will not process interrupted uploads (due to network issues, for example), so you don't find files from interrupted batches in the Content Browser. For those interrupted batches, you can:
Retry the entire set again.
You can access the contents in the notifications area and import those into the Content Browser that did not fail.