COUPON DOESNT APPLY ON THE TOTAL PRICE , IT APPLIES ONLY ON DEPOSIT

hello,

The issue is that when a customer applies a coupon to pay for the product on my website https://www.portraitflip.com/, The coupon is currently applied only to deposit value, not on the total value of a product. Please let me know how to coupon can work on the total value of the item and not just the deposit.

Just to clarify though
So, as a further example, if I had a product at ￡100, with a deposit option of 50%, As a customer, without a coupon, I would expect to pay ￡50 now, and ￡50 at a later date.

A. If the coupon was available for 20% however, 20% be deducted from just the initial ￡50? (20% of ￡50 = ￡10 discount which means in total the customer pays ￡90)

Or

B. the coupon be calculated based on the whole order (20% of ￡100 = ￡20), but then deducted from the deposit (leaving a ￡30 deposit, ￡50 at a later date, meaning in total the customer pays ￡80)

As a customer I’d expect the latter, i.e. receiving the discount against the whole order. Currently, the situation A is happening. Kindly let me know how can I set the situation B to happen.

thanks

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