Cart does not empty after customer places and pays for an order

I have the premium version and i just noticed while testing our site is that when I place an order an iten (in this case one product), pay for it, then we go to the “thank you page”, the cart icon still shows the number “1” on it.

Shouldn’t it reset to zero?

Look forward to your advice.

The page I need help with: [log in to see the link]