CREATE TABLE table_63001 ("Class" TEXT, "Railway number ( s ) " TEXT, "Quantity" FLOAT, "Year ( s )  of manufacture" TEXT, "Axle arrangement" TEXT)

What is the quantity for railway 263?
SELECT "Quantity" FROM table_63001 WHERE "Railway number(s)" = '263'
SELECT "Quantity" FROM "table_63001" WHERE "Railway number(s)" = '263'