Result should return a value greater than or equal to the selected facet
I wasn't able to find answers on how to solve this with Facets alone, or writing custom code which is related to facet API. Honestly, I've been ignoring the most obvious solution to my problem which is Views exposed filter, and this is how I managed to solve my problem:


Create an exposed filter for GPA, which filters result that are greater than or equal to the provided GPA. I made this hidden by default.
I disabled the GPA facet I was using, and wrote my own GPA filter block. It's just a matter of querying the GPA field table, disregarding duplicates.
Wrote a custom script that captures the selected GPA value, from the custom GPA block I created, and then feed it hidden views exposed filter.
I added few more customization to it so that it behaves exactly like the rest of the facets.