Invoice Split

Dear SAP Gurus,

What is the criteria of Invoice split?

I have two items in an invoice. Their pricing date, exchange rate and delivery date are the same. It is an order related billing.

When I create an invoice, its gives me a split, showing different exchange rates.

Exchange rate for letter-of-cr 1.53250 1.51100

The risk management is activated and a Letter of Credit is also assigned to this Sales Order.

I have checked all the exchange rates and at both header and item level 1.51100 is shown. I dont know where is this exchange rate 1.53250 is being picked.

Kindly help.

Regards,

SZ