Check off the boxes you wish to unsubscribe from

In attempting to unsubscribe from a company's emailing list, I was directed to a website with the following form.

Note the phrase "Check off the boxes... you wish to unsubscribe from." Is this some type of standard phrasing? The use of the terms off and unsubscribe seem to make the sentence ambiguous; should I check or uncheck? (The default page has all check boxes unchecked.)

Is there a way this company can improve their phrasing?