Im planning to book a star alliance award to NRT and ICN with the following routing.

15 March SIN-ICN on SQ
21 March ICN-NRT on Asiana
28 March NRT-SIN on SQ

Is this a valid roundtrip star alliance booking with a stopover in ICN?
I assume, based on the star alliance award chart, it will cost me 50K miles?

When I called, I was qouted 62,500 , and I just cant believe it. The agent reply is, that is what my computer is telling.

Do I need to call again and insist that there might be glitch and it should be 50K miles instead?
Obviously the additional 12,500 miles is they charge me separately on ICN- NRT leg?