Just like @lantzgould mentioned. I am just too slow at typing… It is used for matching purposes. From the Bubble Reference:
Ranks a list of things by average RMS similarity of all numerical fields to a target item of the same type. Use this to match people for a dating app for instance."
Here is an example for you:
Editor: 805testapp42 | Bubble Editor
Preview: https://805testapp42.bubbleapps.io/version-test/rankedby?debug_mode=true
For me, the confusing part was to figure out which number it was comparing. Then I noticed it said “ALL numerical fields” so it actually ranks it by ALL of the numbers I saved in the database attached to the user. Hope that makes sense.
Hope that helps! 