CREATE TABLE table_204_590 (id NUMBER, "year" NUMBER, "division" NUMBER, "league" CLOB, "regular season" CLOB, "playoffs" CLOB, "open cup" CLOB, "avg. attendance" NUMBER)

how many times did the usl a league reach the quarterfinals ?
SELECT COUNT(*) FROM table_204_590 WHERE "league" = 'usl a-league' AND "playoffs" = 'quarterfinals'
SELECT COUNT(*) FROM "table_204_590" WHERE "league" = 'usl a-league' AND "playoffs" = 'quarterfinals'