Your pictured Pool Shock is just 12.75% liquid chlorine. It is not stabilizer. You may also find stabilizer labeled as "conditioner" at the Pool Store. Incidentally, that is now the only chemical I buy from a "pool store." Everything else from the local hardware store, grocery store, etc. This site will save you a lot of money and prevent a lot of headaches, rest assured. (Consider becoming a suppoter!)
If you decide to use the 20% Muriatic Acid (which I did) because it's safer to handle and easier to find, note the following from another poster on this site whose name escapes me: "Use the Pool Math app. Select the 15.725% option for your MA calculation. Multiply the indicated dosage by 1.27. (Add 27% to the lower dosage.)"
Works great. Good luck!