Question about Cron setting section


In "Settings->Cron" section I can setup how many email I can send per minute.
This settings applys globally to all of my campaigns or for each campaign?
I mean
I have got 3 campaign of emails, and I setup 30 email per minute in "Settings->Cron". How it will work?
Will it send 30 emails/min for each of my campaing (30+30+30=90)? OR
Will it send only 30 email/min for ALL of my campaigns (about 10 emails per campaing per minute = 30)?