Why my gmail inbox stays at maximum 10

There is lot of discussion on email overload. But for me, the emails remain not more than 10 at any given time!

Why?

- I do get lot of emails. If i do not delete emails, I would get add more than 200 emails per day to inbox!

- How i do it?

Selective Retention, instead of Selective Deletion

- Open gmail - Select all mails === IMPORTANT === - iterate over the email, "unselect" that you need to keep - DELETE

can it be more simpler?