CREATE TABLE table_61371 ("Number" FLOAT, "Time" FLOAT, "Aircraft" TEXT, "Opponent" TEXT, "Location" TEXT)

What number has the opponent Fokker d.vii with a time of 600?
SELECT SUM("Number") FROM table_61371 WHERE "Opponent" = 'fokker d.vii' AND "Time" = '600'
SELECT SUM("Number") FROM "table_61371" WHERE "Opponent" = 'fokker d.vii' AND "Time" = '600'