First of all, M-fares earn MQMs worth 150% of miles flown.

Per Delta, the mileage and MQMs for each segment are:

Boston, MA(BOS) to Atlanta, GA(ATL) 946 Miles - 1419 MQMs
Atlanta, GA(ATL) to Seoul, Korea(ICN) 7156 Miles - 10734 MQMs
Seoul, Korea(ICN) to Tokyo-Narita, Japan(NRT) 759 Miles - 1139 MQMs
Tokyo-Narita, Japan(NRT) to Atlanta, GA(ATL) 6850 Miles - 10275 MQMs
Atlanta, GA(ATL) to Boston, MA(BOS) 946 Miles - 1419 MQMs
Totals for the actual flights: 16657 Miles - 24986 MQMs

Then the Triple Medallion bonus kicks in adding 49,971 MQMs (3 X 16657) for a total of 74,957 MQMs.

By the way, if you're a Gold or Platinum Medallion, you will get an extra 16,657 miles (not MQMs) as your elite bonus.