Good time of day. I would like to ask how the url of the map piece is formed. For example, coordinates 11888 103 -11389 correspond to a piece x2/3/z-2/3.png What is the relationship between coordinates and numbers in the link. Thank you in advance

I recommend asking questions about how BlueMap works in the Discord server. BlueMap's GitHub issues are for actual bug reports only.

remove the /s and you can read it:
x2/3/z-2/3.png -> x23z-23.png -> x23 z-23
which is the tile-coordinate

But yeah like Jelle said .. further questions go on our discord :)