Receipt created via lockbox should not calculate unearned discount

Hi Team,

We have earned discount and unearned discount both enabled in our system.

Customer paid 757.53 and customer has not taken any discount.
Invoice XXXXXXX has due date of 4/12/2024.

But when the receipt XXXX got created with receipt date of 05/03/2024 it applied amount 742.38 and gave unearned discount of 15.15 and this amount went as unapplied.

So what customer is saying that after due date we have 10 days grace period within that date if customer pays we can give discount but after grace period there is no discount.

Kindly confirm what can we do with this use case.

Thank you,
Asif Sayyed