The video title says 15 Qassam rockets intercepted at once, but I think that’s highly unlikely. ID tends to operate on a “shoot-shoot-look” basis. That is, they fire two interceptors toward each valid target. That would put the number of intercepted targets at probably 7. Which is still a pretty formidable barrage.
As always, with any youtube touching even tangentially on Israel, don’t look a the comments. They’re a sewer of ignorance and hate.