그쵸 is a short form of 그렇지요 which means "Isn't that so"

it means "isn't it".

Everyday language~ 지요 -> 죠 For example , formal --------------------------------------------> informal 맞습니까?(is it right?) - 맞지요? - 맞죠? 가능합니까? (is it possible? ) - 가능하지요? - 가능하죠?