This is why you need the switch and the motion sensor as Means to Activate the Room Lighting instance. In @bill.d's example, it's the 6:00 minutes since last Activation Event that would turn off the switch. Basically, if you flipped the switch, you would Activate Room Lighting. There would be a countdown started and after 6 minutes, it would turn off the switch unless there was another activation event.
For your needs, you'll want to also the Activate even if already Activated option selected. If you flipped the switch and do not go upstairs, the switch will eventually turn itself off. If you go upstairs, you'll trigger the motion sensor which would send a new Activation event to Room Lighting and reset the timer. Every time you have a motion activated, the timer would get reset. Eventually, the switch will turn off by either the timer, motion inactivated and stays, or the switch gets turned off.
It will override your countdown from the Last Activation Event and make the motion sensor inactive and stay the priority for turning off Room Lighting. Based on your instance, it is probably not that important to have depending on how long your motion sensor cooldown period is. Based on this Room Lighting instance, this is what should happen:
1.) You turn on the light from downstairs. Your 2:00 minute time starts.
2.) If no motion, your light turns off in 2 minutes
3.) If motion, the sensor will prevent the 2 minute timer from turning off the light. Your motion inactive and stays will take precedent.
4.) In the rare case that your motion goes inactive and starts the "stay countdown", this setting will prevent the 2 minute Last Activation Event countdown from turning off the light. The inactive and stay will take priority.
