A weapon gains critical-hit chance, while another gains critical damage. The names sound related because they are, but they change different parts of an attack. Chance concerns how often a qualifying critical hit occurs; damage concerns its effect when it does.
Actual games can add caps, special conditions, resistances, or different stacking rules. The calculation below is a deliberately simplified example, not a claim about a particular title. OpenStax’s probability introduction provides the underlying distinction between a probability and the observed results of a finite run.
Give the example explicit rules
Suppose every ordinary hit deals 100 damage, a critical hit deals 200, and each hit independently has a 20% critical chance. Ignoring every other mechanic, the expected damage per hit is 0.8 × 100 + 0.2 × 200 = 120.
Increasing critical chance to 30% makes that expectation 130. Keeping chance at 20% but increasing critical damage to 250 also gives 130 in this example. Equal average results do not mean the attacks have identical patterns: one produces critical hits more often, while the other makes them larger.
A short test can differ from the expectation. Twenty-percent chance does not promise exactly two critical hits in every ten attacks. Record enough observations and keep conditions consistent before interpreting a practice session.
When reading a real game’s item, check whether its percentage means total critical damage or an additional bonus. Then look for the official rules or current in-game description governing that attack. Do not transfer the example’s assumptions to an ability that cannot critically hit.
The useful first question is not “which number is bigger?” It is “which part of this attack does the stat change?”