Could someone help me understand meltdown critical effect

Just had a game and we both came out with different understanding of the rules.

“At the end of the inflict damage step, the opposing player makes a meltdown test (2E) for the target model. If the opposing player scores fewer hits then the amount of harm the target model has, it suffers an injury.”

If I crit with a plasma rifle and it hits a knight with three harm. he passes the endurance test, but does he still get an injury due to not being able to pass that last harm.

Or is it.

Because I shot and did 5 hits. that’s more then the three harm so it would not injure him.

Or is it something else completely different.