Complex sentence: Agoonorees are held once every four years, and are abbreviated as "NA", or including the number of the event, as (for example) 9NA for the 9th Nippon Agoonoree.
Split into simpler sentences: Agoonorees are held once every four years, and have currently been held nine times. They are abbreviated as "NA", or including the number of the event, as (for example) 9NA for the 9th Nippon Agoonoree.