I would surmise your SD card is corrupt, or has become corrupted by the Uconnect system. I had the exact same experience when I first got my vehicle. Song counts kept changing every time I got in/out of the vehicle.
Try selecting "browse", then select a folder and scroll up/down and see how many of your songs are showing as duplicates in the display. Guessing most or all, maybe even some triplicates. Yet, when you eject the SD card and insert it into your computer, it will show the correct number of songs. What's even more bizarre, to my non-tech brain, is that you can select any of the duplicate or triplicate entries and they will all play.
Before you get a new SD card, try reformatting the current card (give it a different name also), reload the songs onto it, then use the lock tab on the SD card to lock it before inserting it into the SD slot in the vehicle. See if that works for you. If it doesn't, then try a different card.
In my case, I wound up taking the SD card back to Costco and getting a new one. The current card is locked and the song count is accurate and stable.
Good luck and if you don't mind, I'd like to know how this goes for you. I just have a particular interest in the "media" application and whether or not they fix some of these problems in an update. Problems like not being able to use "shuffle" mode within a folder, or "shuffle" mode not being retained when you stop/start the vehicle. Sometimes it is, most often it is not.