I honestly did not know that one could boost a geocache's favorite points with such exploit.
What Project-GC does is quite simple.
- It checks how many users have given an FP. A log is required.
- It checks how many have logged it, or have given an FP (and has a log). The second part is if they were premium while handing out the FP, but the FP expired.
For this cache, it results in 3 users giving an FP, and 5 premium users logging it. 3/5 = 0.6 = 60%. A number that actually sounds quite correct.
I am surprised that Geocaching.com doesn't handle it correctly though. Is this a new issue? I haven't seen a single geocache where the percentage at Project-GC doesn't agree with Geocaching.com before, and have not heard about this issue, therefore I am quite surprised.
Since I think Project-GC does it in the correct way (which you seem to agree with after understanding what's happening, from reading comments) I don't think we will try to change anything here.
PS! It's super nice with a geocache that doesn't have 50+ logs when analyzing FP issues. Quite fast to calculate this one manually.