CREATE TABLE table_203_330 (id DECIMAL, "year of election" DECIMAL, "candidates elected" DECIMAL, "# of seats available" DECIMAL, "# of votes" DECIMAL, "% of popular vote" TEXT)

how many more seats were available in 1975 than 1963 ?
SELECT (SELECT "# of seats available" FROM table_203_330 WHERE "year of election" = 1975) - (SELECT "# of seats available" FROM table_203_330 WHERE "year of election" = 1963)
SELECT (SELECT "# of seats available" FROM "table_203_330" WHERE "year of election" = 1975) - (SELECT "# of seats available" FROM "table_203_330" WHERE "year of election" = 1963)