That's measuring by meal count, which I believe is most practical.
Well, maybe most practical in terms of supporting your idea that you are 80% vegan, but I think a more representative way would be to look at the food consumed over a larger time, say a month. I could just as easy argue that I am 95% vegan, as I spend less that 72 minutes a day eating, but when I eat my diet is 100% animal based. if you are vegan, you dont consume animal products, if you are not vegan the chances are you are a omnivore. Being 80% vegan is functionally equivalent to not being a vegan. Most folk would just say they don’t eat much meat, but I suspect you think "80% vegan" says something better about yourself.