Refund Amounts - It makes no sense at all

Does anybody actually understand how Amazon refunds actually work, I'm sure they make it as complicated as possible.

A recent example;

We sell a product for £14.99 + £3.99 Shipping giving £18.98

Amazon takes off the following;

Product Commission £2.25 + £.045 tax = £2.70

DSF £0.06 + £0.01 tax = £0.07

Shipping Commission £0.60 + £0.12 tax = £0.72

So we are paid £18.98 minus charges £3.49 = £15.49

A week later we get a refund request, ' the customer didn't need it after all'

So Amazon debits our account with £3.35 for a label

Then the customer returns the item and our account is debited the following;

Product refund -£10.17

Product Tax refund -£2.03

Shipping tax refund -£0.67

Shipping refund -£3.32

Refund to Buyer -£16.19

So the customer paid £18.98 for the order and is refunded £16.19, the difference is the cost of the label , but the label is £2.79 + VAT = £3.35, so why is the customer only charged the net amount and I am charged the gross amount?

It gets worse;

Amazon credits me for

Commission: £1.83 + £0.37 tax = £2.20

BUT WAIT A MINUTE I was charged £2.70 commission on the order, so why am I being refunded me 50p less than I was charged

Digital services fee: £0.05 + £0.01 tax = £0.06

BUT WAIT A MINUTE I was charged £0.07 DSF on the order, so why am I being refunded me 1p less than I was charged

Shipping Commission £0.60 + 0.12 = £0.72

This is the only amount that is the same as the amount charged on the order

AND TO CAP IT ALL I am charged;

Refund commission: -£0.49 + £0.10 tax = £0.59

So total charge to our account -£13.80

So hopefully you are still with me

As a result of a change of mind by the customer we are out of pocket for the cost of the outgoing postage plus

the difference between the net amount we received from the order £15.49

and the amount debitedd from our account -£13.80 - £3.35 = -£17.15

So we have lost out on £15.49 - £17.15 = -£1.66 on a no fault refund, surely the amount of the refund to us should equal the amount that we were paid for an order, not £1.66 more!

Can anybody explain what is going on are is Amazon scamming us?