Hey Hadas, the grid snapping not lining up is either because it’s snapping the object origin and not the vertices (which is to be expected in object mode) or because you need to turn on absolute grid alignment (next to the increment icon).
As for the size, try applying the scale with Ctrl+A. Changing the cube in edit mode won’t change the object’s scale, but it will change the dimensions, which is shown below the scale in the viewport properties under transform.
Hope that helps!
