"% chance to gain a (flask) charge on kill" --- buff or nerf?

All Flasks say "refill at wells or by killing monsters"

What is the "normal" unbuffed chance to generate a charge?

POE1-wiki says: "a normal monster grants 1 charge, a magic monster grants 3.5 charges, a rare monster grants 6 charges, and a unique monster grants 11 charges"

If POE2 has the same base, then "28% chance to gain a charge on kill" would be a HUGE nerf to chage generation if it *replaces* that charge generation.

If it's an increase, how does it work?

From what I can tell, it's a percent chance for an *additional* charge on kill. This makes it rather pointless for bosses and rares, but may make sustain a bit easier while clearing if you're having trouble keeping up with flask charges getting to them.