CSB: Retainage based on amount > Schedule of Value

We have a situation where the billing amount of an invoice created in Contract Billing exceeds the amount of the schedule of value.  There is only one billing line (unit price) involved.  The invoice is created with the correct amount except for retainage which stops calculating at the % times the schedule of value amount and not the invoice amount.  Is this functioning as designed?

Example:

1.  Schedule of Value Amount $100 (based on 1 unit at $100 unit price)

2.  Invoice Amount $300 (based on 3 units at $100 unit price)

3.  Retainage % set at 10% of contract up to 100%

4.  Retainage amount calculated in invoice created by R52121 was $10 (10% of schedule of value)....we would like it to be $30 (10% of invoice)