What's the total number of NGC that has a Declination ( J2000 ) of °15′55″, and an Apparent magnitude greater than 10?
CREATE TABLE "6401_6500" (
  "ngc_number" real,
  "object_type" text,
  "constellation" text,
  "right_ascension_j2000" text,
  "declination_j2000" text,
  "apparent_magnitude" real
);
SELECT SUM("ngc_number") FROM "6401_6500" WHERE "declination_j2000"='°15′55″' AND "apparent_magnitude">10;