When using PayPal, a mysterious Fee is being added

I have my events set up so that if someone registers and they are a member, it is 100% free. If they are not, then they pay for the full tuition price and go to PayPal to check out.

I was just testing my system and there is a mysterious $500 extra fee being added that I have not input or generated anywhere.

see attached image.

Where is this coming from and how do I get rid of it?

here's the link: scrttc.com/index.php/registration/register-now.html

As I mentioned in Skype chat, the amount is added by a custom fee field which you setup in Registration Form. The solution for the problem had been provided via Skype .

Tuan