The "Number" represents the approximate but not exact number of prongs, and the more prongs, the more froth or foam it produces. However, this is not an indication of better quality as some schools of tea ceremony frown upon froth. The biggest school of tea ceremony, Urasenke, teaches that an even level of froth is desirable, and so this has become standard among non-practitioners.
常穂・並穂 Joho or Namiho
数穂・繁穂 Kazuho or Binho
八十本立 (No special name, characters mean "80-prong")
百本立 (No special name, characters mean "100-prong")
百二十本立 (No special name, characters mean "120-prong")
NAME: Matcha Bamboo Whisk 72 DIAMETER (bottom): 2.2 cm (0.87 in) HEIGHT: 11 cm (4.33 in) Measurements above are approximate
MATERIAL: Bamboo NOTE: Color may not be exactly as photographed. ORIGIN: Made in Japan