NetWatch: Is it a bug or do I not understand

I experience some behaviour with netwatch I don’t understand.

I am checking an IP address with an interval of 1 minute (the default) and when the IP goes down/up it will send me an email.
That functions as expected.
But I have put the timeout to 600000ms (10 minutes) because I don’t want to get notified if the IP is back within these 10 minutes.
But the strange thing is that I receive an email in about 55-65 seconds after I manually make the IP unavailable.
Is this the normal behaviour?

Obviously I can put the interval to 10 minutes and leave the timeout around 1000 ms (default) but is that than the way to go.
I would think I can check it on a short interval and only consider it down after the configured timeout.
This is just as described on the Wiki pages.

Netwatch takes action whenever it detects a state change from its last saved state. Watch the state of netwatch and do the test again.