[glassroddr]

The knotted leader is made up of different size monofilament lenghts that are tied to create a taper, starting with the end that is tied to the flyline (butt)and adding mono of smaller diameter toward the tip and finally the tippet. The knotless leader is one continuous length of mono that tapers to a tippet. The numbers in the formula you're mentioning is that 60% of the lenght is the butt section, 20% is the taper or middle section and the other 20% is the tippet. The longer the butt section is, the better it will cast a large fly, as opposed to a shorter butt and longer taper or middle section will delicately cast a small dry fly to rising trout. When you tie your own leaders, you can try out different formulas and adapt them to your fishing. Hope this helps.