Ask to ticket it as a roundtrip with the free stopover, and ask for a supervisor to verify the 50k miles is correct. It seems some agents are not well versed in the free stopover concept. I got the same crap that they ticket as separate legs when I tried to ticket my SIN - FUK - HND - SIN flights. Insisted on the free stopover, and agent says will consult with supervisor. Called back with the correct miles for roundtrip plus free stopover.