DON'T UNDERSTAND "DELL DIAGNOSTICS" RESULT (Finds Same Drive Twice?)

I have just run "Dell Diagnostics" on my Dell XPS9000 machine. It found "ST2000DM001-1CH164 ATA Device", which I assume is my C: Drive. All categories said, "Passed".

Then it found something called "ST2000DM 001-1CH164 USB Device", which has the same name as my C: Drive, but calls it a "USB Device". The first two categories here said, "Device Not Found". But the rest of the categories said "Passed". If the device is "not found", how can it have passed the other categories? And just WHAT is this device that has the same name as my C: Drive??????

Is something failing on my computer??