is turned on for x minutes -> is it "for", or "for or more then"?

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Sorry if this is in the documentation or the forum somewhere. I could not find it.
I have a central heating rule with a “swing” value of 0.3 degrees in it to prevent overshoot when heating up

if $livingroom-temperature >= ($thermostat.temperatureSetpoint-0.3) and heating is turned on for 15 minutes then turn off heating

What I want it to do is to turn off the heating when close to the setpoint and being on for 15 minutes or more.
Is that what the rule does?
Or is it really: when it is exactly “on for 15 minutes”?

It is really hard to simulate or play with it.

Edit: To be absolutely sure I also have

if $livingroom-temperature >= ($thermostat.temperatureSetpoint)  then turn off heating

To make sure that it does not continue heating.

@Harry-van-der-Wolf

If … Is turned On for 3 minutes = 3 min or longer

If trigger: … Is turned On for 3 minutes = exact 3 min

I’m not sure if I completely understand.
If you take a look at my rule then is that an If or a trigger?
Or does it need to be between brackets?

if [$livingroom-temperature >= ($thermostat.temperatureSetpoint-0.3) and heating is turned on for 15 minutes] then turn of heating

It is a IF
It is only a trigger if you use the word trigger.

Thanks.
My rules are based on your Koffie’s tweakblog, so thanks another time.
I learn every day (and also forget every day)