The Nashville school shooter's ankle bracelet

Audrey Hale's autopsy report says she had a bracelet around her ankle with the number 508407 written on it. The police still haven't figured out what that was for. I was wondering if anyone knew.
Except for that, and the four bullets that hit her, it is a pretty normal report. (One of the bullets went through her aorta and both of her lungs. Another one broke her leg.)
You find out a few details about Hale herself, like no evidence of drug use and she took good care of her teeth. The report is kind of long, over 10 pages, but it's a bit interesting to know.

This might be a good time to point out, I haven't come across any major school shooting where the shooter was on illegal drugs at the time he/she did it.