Yes, I just watched the video again and now understand I was getting resistance confused with RPE.
No wonder I couldn't get past 15mins! (although I am a complete NOOB!)
Thanks.
I worked out it takes 5 full turns of the tension knob to get from slight resistance (1) to nearly full resistance (10)
So, I'm using each half turn to increase by 1.
Using this method will mean a 3 is one full turn.
It's not a perfect method, but might help...