Formula not auto updating

Only calculates when I update/publish my post, is there a way to do this while I put numbers in? I’m using this to make sure my numbers add to 100 with 3 fields. Right now say I have x=50, y=25, and z=25 but on a different post (that I just duplicate) I need x=50, and y=50. It won’t work as the total field says it’s at 125. Even when I delete the z value it won’t save my post.