Tiles. There is a correct way to install them. I don’t know how you decide what’s correct, but sometimes it’s centred, sometimes a full one on the left, or the right.
Then you have the same scenario but top to bottom.
Then you have the same scenario but top to bottom.
A few suggestions for your tool. Add millimeters as an option. I'm using 12"x24" tile for the floor but they're really 300mm x 600mm. I learned most 12"x24" are that size. Another thing I learned is with that size it's recommended to use a 33% offset pattern. This guy explains it well https://www.diytileguy.com/12x24-tile/