CREATE TABLE table_53981 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

What was the size of the crowd when the away team scored 6.15 (51)?
SELECT "Crowd" FROM table_53981 WHERE "Away team score" = '6.15 (51)'
SELECT "Crowd" FROM "table_53981" WHERE "Away team score" = '6.15 (51)'