Basically, it's reading your personal preferences for ballpitBonus. If you have 350 balls in the pit, set your ballpitBonus to 35 and all should detect modifier properly from there on.
The issue is that your preference doesn't appear to correctly be updating currently though, at least not for you... Appears that it's supposed to automatically update, based on consequences.txt, but the default if the autodetection fails is 1% (found in defaults.txt).
Basically, someone needs to troubleshoot consequences to make it actually work properly for detecting percentage.
ETA: also, when does mafia check the description text for consequences? On login? Ascension? Clan hopping?
The only guarantees I see are
1) it will check when you display the effect description (by clicking on the effect icon, or manually going to the proper desc_effect.php? page)
2) it will *not* detect that somebody added some balls behind your back
To clarify, I hadn't hopped clan in a week or two, No balls have been added in a few months, I hadn't ascended for nearly two weeks, and I login in multiple times a day. Visiting the effect description didn't change the results.
Though oddly in 8820 it does seem to be picking it up correctly at present.
The ballpit bonus is updated when you look at the description of the Having a Ball effect, and I've just double-checked that this actually works. It intentionally doesn't pay attention to the ball count shown on the pit itself, since that's not necessarily relevant - you could have jumped into a different clan's pit.
Would it be possible to get a CLI command those goes through and does all of these updates? Like, checks your crimbo tree if you've got one, checks your necklace, checks your slime skills or whatever else works that way. Just makes sure everything Mafia knows is up-to-date.