If you create a single order, the default is that your user ID is the same as your email address which was used to place the first order. If you make subsequent orders and do not use your original user account, a new account will be created and your User ID will be equal to your email address with a suffix β-1β.
If you continue to generate new accounts using the same email address, the suffix will be β-2β and so forth.
For example, if an order is placed with email address example@example.com, the user ID for the second order is example@example.com-1