For tracking the power on time of our machine, we are sending a time on variable that injects initially upon startup, and then just prior to a routine shutdown, it sends a time off variable. These are simply true values or just 1 in Ubidots. I would like to then proceed to take the difference (Time Off - Time On) to add up the total runtime of the machine. Is there a way to create a synthetic variable and do that math with the timestamp? Or does the value sent have to be a timestamp? When I send a timestamp value its in UNIX/Epoch time I believe and is in the hundreds of thousands. Looking for the best way to do this, I am sending from Node-Red btw.