Hi Arnold! As @guitarenthusiast says the tempos weren’t intended to mean anything - they’re just intended to be in the general ballpark of whatever I played. Some may be more accurate than others.
When it comes to learning motions, smoothness is what matters, and when you’re new and still learning the motion itself, you can usually only feel that when playing fast. Meaning, you start with the fastest you can play and make small adjustments to your form until you feel it “click” and become smooth. You can start to slow it down later to become more conscious of the motions and clean them up. This is how I think most people learn to play fast, i.e. by starting fast, finding the “click”, and then slowing it down. Teemu Mantysaari mentioned in our interview yesterday that this is how most of his students first grasp a particular picking motion he’s showing them.
So I wouldn’t do the “working up” to speed, I’d do the far more wordy “starting fast and smooth and working very slightly down to accuracy, while continuing to also make fast attempts to see if they also become more accurate over time”.
And as @tommo points out, random variation throughout this process keeps things fresh and gives your brain enough chances to do it right and to recognize what doing it right feels like.
