Tracking unique visits

The piwik page say:

“If a visitor comes to your website for the first time, or if he visits a page (or downloads a file) more than 30 minutes after his last page view, this will be recorded as a new visit. A Unique Visitor can make multiple Visits per day.”

But the tests that I ran through Piwik showed me that after 30 minutes I should be considdered a new visitor but I still saw the same number and it did not look as if I tracked in piwik.

I mean if more than 30 min. passed between each one of my visits, it should be counted towards the total visits, right?
This doesn’t happen. Where do I look?

Can you describe what happens exactly and what you expect to happen instead?