@Bay Mud Thanks for pointing it out, it's amazing how one can spend ages writing an app and miss obvious things until somebody points them out. Then you wonder why nobody else has🙂 This appears to be that bad habit of programmers counting from zero, so you go 0, 16, 32, 48 but when you're counting from 1, as with patch numbers here so it's 1, 17, 33, 49...
I'll sort this out and post an update to the Microsoft Store over the next few days.