When entering your card details you see one or more unexpected characters pre-populated in the fields.
For example, if your address contains an ampersand character (&), this will be pre-populated in the payment form as '&'. Example:
First seen in
Characters such as double quotes ("), single quotes ('), ampersand (&), greater/less than (<,>), etc., are converted to HTML entities during the population of the payment form.
What To Do
You can change the values as you see them in the payment form and this will not affect the transaction.