Collection letter sent when the score reaches below the threshold

Summary: We have configured for collections scoring and the letter are sent to customers based on scoring. The score is based on amount due remaining greater than 100. The customer should receive the letter only if the total amount due is greater than 100

After the first letter is send the customer pays few invoices and now the balance is less than 100 ($48), the customer should now stop receiving the dunning letter. But we observed that the letter is still sent to the customer even though the balance is 48. How do we ensure that the customer stop receiving the letter as the score of the customer is below the threshold of sending the letter