What criteria do you use when you are counting the number of countries you have been to?

I was just recently counting the number of countries I've been to, the rule of thumb I use is unless I spent the night there I don't really count it. If I drive from Paris to Amsterdam I'm probably not going to count Belgium as a country visited if I just drove through it.

But at the same time I definitely count the Vatican as a country I've been to even though it's not a country you can necessarily spend the night in

I started thinking about this a little bit more as I started to collect flag patches based off every country I've been to. And then I got to Hong Kong. I'm having an internal debate on whether or not I should consider Hong Kong its own entity for travel purposes versus China. Especially with the historics involved I feel like it could go either way.

What is your guys's criteria on what you count as a country and what you count as a visit. And what are your thoughts about counting Hong Kong and China as two countries or just one?

I also see this type of internal debate coming up when I start visiting British overseas territories which I may count as their own country collectively separate from the UK.