This what Mazon replied.
“I'm sorry your order did not come with all 6 of the Swiffer products.
I've requested a refund of $5.98 to your original payment method.You'll see the refund on your credit card statement in the next 3-5 business days.
I've also issued a $10.00 promotional certificate to your Amazon Prime Now account, which will automatically apply without a claim code the next time you place an eligible order on Amazon Prime Now.”