The Premium Proportional field (tag 4526) is only a viable option when you recognize OID amortization.
If the Premium Proportional field is set to Yes, Eagle Accounting nets the values of the acquisition premium stream and OID amortization steam on the general ledger (for OID eligible bonds purchased at a discount, but still above the adjusted issue price). Eagle Accounting tracks the acquisition premium and OID amortization separately on the sub ledger.
Eagle Accounting calculates the acquisition amortization premium stream daily delta in proportion to the amount of the OID being recognized. Eagle Accounting uses the following formula to calculate the acquisition premium daily delta:
Total Acquisition Premium to be Recognized
------------------------------------------------------------------ = Acquisition Premium Daily Delta
Total OID Amortization to be Recognized

If the Premium Proportional field is set to No, Eagle Accounting tracks the acquisition premium and OID amortization stream separately on the general ledger and sub ledger. Eagle Accounting adheres to the applicable amortization method being used for OID amortization.
An example follows.

Premium Proportional Example

A position has $10.00 of Daily Acquisition Premium Amortization, and $100 of OID Amortization.
If you set Premium Proportional to No, Eagle Accounting creates the amortization general ledger entries shown in the following table.

If you set Premium Proportional to Yes, Eagle Accounting creates the amortization general ledger entries shown in the following table.