One-Triggers-Other (OTO)

Imported from previous forum

“The Initiator enters two orders in a single transaction and states that there should be an OTO contingency between them. One of the orders is marked as the primary order and the other as a secondary order.”

For OTO How does one indicate the primary order in the repeating group? The only thing i could think of was the primary has to be to be the 1st ListSeqNo of TotNoOrders.