If for some reason you need to amend, partially refund, or cancel the order made for your school photos using the Pay In Four option – the refund goes back against the repayments in place with PayPal.
If your refund is partial- it will still be applied to your payment plan, starting with the last installment scheduled first. Therefore if the refund amount exceeds the payment due on the fourth installment, your third installment amount will be further reduced, and so on.
Need further information – please check https://www.paypal.com/au/webapps/mpp/paypal-payin4/shortterms