CREATE TABLE table_203_568 (id DECIMAL, "town/village" TEXT, "population" DECIMAL, "postal code" TEXT, "municipality" TEXT, "island" TEXT, "location" TEXT)

how much greater is the population of argir than glyvrar ?
SELECT (SELECT "population" FROM table_203_568 WHERE "town/village" = 'argir') - (SELECT "population" FROM table_203_568 WHERE "town/village" = 'glyvrar')
SELECT (SELECT "population" FROM "table_203_568" WHERE "town/village" = 'argir') - (SELECT "population" FROM "table_203_568" WHERE "town/village" = 'glyvrar')