The grid scale can be anything, but to expand the grid size you need to add a border all the way around, and that means adding 2 rows or columns at a time. (One on the negative axis, the other on the positive) These can be even or odd, but they need to increment by 2.
If you have odd numbers, then the center will always fall on 0, which is probably what you want. You just have to increment by 2 each time.
For example,...draw a grid on paper,... then try to add a single line. You will see that you need to add one to each side, or you will be making one side bigger than the other. (Unless the grid shifts, which you stated you don't want)
If you have odd numbers, then the center will always fall on 0, which is probably what you want. You just have to increment by 2 each time.
For example,...draw a grid on paper,... then try to add a single line. You will see that you need to add one to each side, or you will be making one side bigger than the other. (Unless the grid shifts, which you stated you don't want)