You can use up to $200 of your Afterpay overall available to spend amount on eligible transactions for Retro orders. For example, if you have an Afterpay available spending limit of $1,000, you can use up to $200 for Retro orders and the remaining $800 for any other Afterpay Buy Now Pay Later purchases.
Please note that your overall Afterpay available to spend amount doesn’t change with the use of Retro - it will just form part of the limit.
Refer to here for further information.