CREATE TABLE table_203_577 (id DECIMAL, "tenure" TEXT, "coach" TEXT, "years" DECIMAL, "record" TEXT, "pct." DECIMAL)

how many more years did d. v. graves serve compared to j. f. jenkins ?
SELECT (SELECT "years" FROM table_203_577 WHERE "coach" = 'd. v. graves') - (SELECT "years" FROM table_203_577 WHERE "coach" = 'j. f. jenkins')
SELECT (SELECT "years" FROM "table_203_577" WHERE "coach" = 'd. v. graves') - (SELECT "years" FROM "table_203_577" WHERE "coach" = 'j. f. jenkins')