It's 100 swings. Do ten with one hand. Set the bell down. Rest. Pick bell up with opposite hand. Do ten swings. Repeat this process until 100 swings are done. Any variance in the book is simply building up to this - 100 swings, in sets of ten, using the one-arm swing. Some people are still perfecting their one-arm swing, so two hand swings are still mentioned, as are hand-to-hand swings, along with a protocol for phasing them out.