Folder names in the 2013 GPS data

Hi,

I am using the 2013 GPX planet data of OSM in the link below for the purpose of my research. (https://planet.openstreetmap.org/gps/)

I downloaded the tar file and extracted it to my workstation. I found out that there are folders that have names of systematic numbers, and I am wondering what the folder names mean. For example, there are '000' and '001' folders in the 'identifiable' folder and each folder has folders named '000', '001'...'990', which have some gpx files. Is there someone who can explain the meanings of folder names?

Also, I am wondering if there is a way to use the recently uploaded GPS data in OSM for the research purpose. I would appreciate if you could let me know the contact info for that.

Thanks,