Hello, Good question. If you count up, use 4 "shi"and 7 "shichi". But use the opposite when counting down. So 5, 4, 3 is "go", "yon", "san". And 8, 7, 6 is "hachi", "nana", "roku". Also when using counters for counting various things, then you want to use "yon" and "nana" and their variations given different objects and things. You can see one (basic) example here: https://www.learn-japanese-adventure.com/image-files/t3-japanese-numbers-special.png Hope that helps.