[Projectile] [Attack|Attacks] have a (8-12)% chance to fire two additional [Projectile|Projectiles] while moving

What this record tells you

This is a suffix modifier available from level 65. Its listed spawn tags determine which item families can naturally receive it.

Positive spawn weight means the modifier is eligible for that tagged item family. A zero weight blocks it for that tag. Weight is relative—not a simple percentage by itself.