"Total number of turns = 20" means exactly what it says. 20 turns in total on the coil.
The 20% is in reference to the height/length to diameter ratio of the coil. The coil is 20% high as it is wide. If diameter = 100cm then height = 20cm.
"Knowledge is cosmic. It does not evolve or unfold in man. Man unfolds to an awareness of it. He gradually discovers it." - Walter Russell
"Once men died for Truth, but now Truth dies at the hands of men." - Manly P. Hall