That would be a bulk/consolidator fare which only qualifies for 25% mileage on a T fare. That's the risk you take when going through a TA. Just because the TA booked you on a published fare to LAX doesn't mean the fare to PEK was also published (the 3 day layover would cause a fare break). Sorry.

http://www.delta.com/content/www/en_...ion-fares.html