CREATE TABLE table_203_104 (id NUMBER, "athlete" CLOB, "nation" CLOB, "olympics" CLOB, "gold" NUMBER, "silver" NUMBER, "bronze" NUMBER, "total" NUMBER)

how many more silver medals did gillis grafstr m have compared to sonja henie ?
SELECT (SELECT "silver" FROM table_203_104 WHERE "athlete" = 'gillis grafstrom') - (SELECT "silver" FROM table_203_104 WHERE "athlete" = 'sonja henie')
SELECT (SELECT "silver" FROM "table_203_104" WHERE "athlete" = 'gillis grafstrom') - (SELECT "silver" FROM "table_203_104" WHERE "athlete" = 'sonja henie')