Photo count discrepancy

Items are usually media files in your Photos Library, that are neither video nor photo, for example sound files.

The "1 item" in my library is a mp3 file:

Did you save photos from the internet or from mail or messages to your photo library on the iPhone? You may have save image files to the camera roll, that are in a format that cannot be processed by Photos - for example tiffs with an unusual color profile or high resolution or unsupported graphics formats.

The numbers of photos may also differ, if you are having bursts in your library, but are not uploading all photos of the burst.

Everything is not loaded and you are low on disk space according to the images you posted - you need to resolve the disk space issue and see if the upload will complete and everything will finish syncing - the problem may also be the 1 item not uploaded - it may be something that can not be uploaded and could stall the process until it is removed and the download does not occur until the upload is complete

LN

How much free space do yo have on your boot drive? It's strongly recommended that one maintain a minimum of 10-15 GB for optimal system and application performance. Shoot for the high end.