CREATE TABLE table_8488 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Ground" TEXT, "Date" TEXT, "Crowd" FLOAT)

What's the average crowd size that had an away score of 15.17 (107)?
SELECT AVG("Crowd") FROM table_8488 WHERE "Away team score" = '15.17 (107)'
SELECT AVG("Crowd") FROM "table_8488" WHERE "Away team score" = '15.17 (107)'