This draft has a repeat of 20 ends made up of four groups of five. To keep track, I tie each group of five into a slip knot, then when all four groups are threaded I tie them all into a bundle. That way I know all four groups have been threaded and I can start the next repeat.
Some people use different methods to keep track. Every person has to figure out what works best for them because we process information differently. What works for one may not work for another.