What is difference between Lishi SC1 and SC4?

SC1 is a 5 pin key, SC4 is a 6 pin. Unfortunately, an SC1 key blank is too short to operate a lock keyed to SC4.

What does SC1 mean on a key?
If you have more than one keyed lock on your home, you may want to use the same keyway in all of the locks. This allows a locksmith to key all of your locks to the same key, which means the same key will operate all of the locks in your home. KW1 represents a Kwikset KW1 keyway, and SC1 represents a Schlage SC1 keyway.