problems with notification

Hello,

I have a problem with notification.
For my needs, I created an alert with the following functions: down service - send an email within 15 minutes after.

Notification have the option to delay, and where I put up 15 minutes.

BUT, when suddenly, the service is restored for the time delay, for example in 3 minutes after the fall,
I still get a letter within 15 minutes of that service in Down, though he was running 12 minutes as.

Is it possible to somehow get around this situation, that dude did not send an alert to drop the service because it actually works?

I am on 4.0 beta 3.

Thanks,
Dmitriy.