RPE is a scale from 1-10, where 1 means you aren’t pushed at all (essentially you are asleep) up to 10 which is a flat-out, 100% effort. If you aren’t sure how hard a 10 feels, try completing 20 burpees in 30 seconds and see how you feel. While this may seem like an unreasonable target, by pushing yourself that hard you will know what a ‘10’ feels like.