Can someone explain the echoing blades talent to me as it's worded weird?

Trying to make a fan of knives build for battlegrounds to make the spec more fun and I can’t make sense of this trait.

“For each of the first 5 critical strikes.” What does that even mean?

Example would be if you are sitting in a pack of 30 mobs with 100% crit chance and you cast fan of knives, only 5 of those out of 30 will proc the trait.