It is kind of a weird fee structure. I guess he's paying more to invoice my payments.

Square’s standard processing fee is 2.6% + 10¢ for contactless payments, swiped or inserted chip cards, and swiped magstripe cards. Payments that are manually keyed-in, processed using Card on File, or manually entered using Virtual Terminal have a 3.5% + 15¢ fee. Invoices cost 2.9% + 30¢ or 3.5% + 15¢ if processed using Card on File.