Travel to US question (Tier 4 Student visa)

Hello everyone,

In the tier 4 student visa online application, It's asking me if I ever travelled to the US, Australia, NZ or European countries in the past 10 years.
I am a US citizen and I have never been to Australia, NZ or European countries in the past 10 years. I have been living in the US for almost two decades. I visited Asia once for a few days few years ago.

They have options from zero to 5-6. What to choose!?

Thanks

Is it not just a matter of fact, whether you have visited those countries or not?