I did the other way round. I first make sure the driver is in full closed position, triple click the button and it will move slightly till it hits the stop position and sounds a long beep. Then, I manually pull the curtain all the way to fully open position that I want and it will sound another long beep and this will be my full opened range.
This is how I set the travel range and I only have one driver at the moment. The second one is in shipment. But I think the same procedure should apply even with dual drivers according to the manual.
I did find the manual tells the different thing as it says it will move itself towards the full opened position and set the opened position when you pulled the curtain by ~10cm. For my case, it didn’t move and I have to manual pull them.
Hope it helps.