nothaseo You might have an array called 'levels' with width = 10 stored in local storage (if you set the width to 10 the first time you ran it or even something you saved in a different project).
It might be a good idea to set the size of the array to (12, 2, 1) after loading it. That would also be a good idea if you wanted to add more levels later while keeping your old saved values.
And also use a more descriptive name like 'mygamename_levels' because you could have many projects storing a value called 'levels' in local storage.