CREATE TABLE table_64438 ("Match" FLOAT, "Date" CLOB, "Competition or tour" CLOB, "Ground" CLOB, "Opponent" CLOB, "Score1" CLOB)

What match number has a ground of H and the opponent Chelsea under 18s?
SELECT AVG("Match") FROM table_64438 WHERE "Ground" = 'h' AND "Opponent" = 'chelsea under 18s'
SELECT AVG("Match") FROM "table_64438" WHERE "Ground" = 'h' AND "Opponent" = 'chelsea under 18s'