Kaom's Way with 20% Fertile Catalyst does not go to 0.5% Life regenerated per Endurance Charge

Creating a Kaom's Way ring and setting the Quality to 20% with Fertile Catalysts leaves the Life regnerated per Endurance Charge at 0.4%, although it should go to 0.5% (I checked on the official Trade website, that this value is indeed reachable).

I also manually edited the Quality value to increase it further. What's strange is that until 24%, the value stays at 0.4% and then it jumps to 0.6% at 25% Quality (this is the point where it would reach an even 0.5% without rounding).

I'm not completely sure what the underlying rounding process should be, but here are some breaking points I found on the official Trade website:

12% Quality --> 0.4% Life regenerated per End. Charge (0.448% unrounded)
13% Quality --> 0.4% Life regenerated per End. Charge (0.452% unrounded)
15% Quality --> 0.4% Life regenerated per End. Charge (0.460% unrounded)
17% Quality --> 0.5% Life regenerated per End. Charge (0.468% unrounded)
20% Quality --> 0.5% Life regenerated per End. Charge (0.480% unrounded)

As you see, 13% should be the breaking point if it is rounded to one significant digit, but for some reason 17% (or 16%, but I could not find that value anywhere) is the breakpoint (all assuming the trade site is correct, can't test this myself atm, though).

No file, test, or entry point is named. Reproduce Kaom's Way with Fertile Catalyst quality values around 12–25%, then locate the item-stat calculation and rounding path for life regenerated per Endurance Charge. Done means the displayed breakpoints match the reported Trade values, including 20% quality showing 0.5% rather than 0.4%.