Duration in Alert function

I am wandering, can anyone help me out in this. What does the Duration really mean in Alert function. I hope the duration would be, for example

I would like to check the one Protocol processes status is up or not,

with comparing the status is up or not, i would like to put 20 mints in the duration, and hoping Cloeverleaf will check the specific process protocol status every 20 mintues and send me a mail if the test condition is true? Will interface do above or something else?

Thanks