Allocation of payment across multiple credit purchases

Description

Hi, I am trying to find out how my monthly payment is allocated across multiple credit purchase agreements. I bought some goods using PayPal credit and spread the cost across 12 months and I also have a purchase offer of interest free fro 4 months and then there are two no offer purchases. I calculated what th instalment should be for the various agreements and paid that. How do I know if the instalment will be a located correctly across the agreements.