Several states in united states have a law for gift cards tender i.e. after gift card tender if remaining balance on the card is below threshold, it must be given as cash to customer in same transaction. Threshold varies by state, some states have it as $3, some $5. 

Example: 

Transaction balance is $10

Credit card tender $1 (partial tender)

Gfit card tender - requested for $9 but it was approved for $12 because after $9 remaining balance goes below threshold of $5, so entire balance left on gift card is approved by payment gateway. 

$9 is applied to transaction at point of sale and $3 is issued as cash to customer.

In this scenario when OMS creates invoice, no where it shows $1 credit card tender. all tender lines described above are not recorded in invoice, it makes transaction out of balance.