Checkout Option - Guest Checkout

Not sure if I understand the Guest Checkout option - as if a customer uses Guest Checkout once - he cannot use Guest Checkout again or Register Account as Email id is in use -
Seems that a customer should be able to do many Guest Checkouts and if he decides later to Register he should be able to - as his email has never been used as a Registered user -

Hopefully I am misunderstanding this and there is a way - so customer can make many orders as a Guest Checkout with same email address -
Please help

Hello John,
Yes, you was misunderstanding. Following is the way that EShop checkout works: If a customer uses Guest Checkout once, then they CAN use Guest Checkout again many other time. He can also register account with the email that he used before. The email is only limited once they register account. So he can not register again with an email which is used to register another account before.
I hope that my explanation is clear.
If you need any more helps, please don't hesitate to let me know.
Sincerely, Giang