The box takes the cell's font color and scales with its font size, and sits centered on the line the cell's text would paint in. Under General alignment it is centered, as Excel centers a boolean; an explicit left or right alignment moves it to that edge. A formula cell draws the box but takes no press: it is drawn disabled, and a press on it selects the cell as a press on any cell does.
The checkbox cell control:
TRUEdraws checked,FALSEand blank draw unchecked, and a press on the box writes the other.