Grid)
A common grid size in timber panel construction is 62.5 cm. The structural timber in the core of the exterior walls is usually positioned centrally at the intersections of the grid lines, so that a stud thickness plus two total thicknesses of the outer cladding results in a typical calculated "overhang" of the exterior lengths over an integer number of grid units. In your case, the exterior walls are probably rather aligned on the outside of the grid lines, 12 units + 2x 29.5 cm = 8.09 m. 9.34 x 9.965 m would be a floor area of about the same size "towards a square" in the same grid.
Bathroom 18 sqm)
Such a size can quickly arise when a design with a gable roof without a knee wall is transferred "1:1" onto a 2m knee wall. With two washbasins, corner tub plus shower, bidet and enough space so that mom is not bumped while putting on mascara, such a floor area already comes together without a knee wall.
Moreover, a typical approach in still inexperienced layperson planning is to initially allocate reasonable individual areas for certain rooms from a floor area; not infrequently, this leaves too much space for the bathroom, and a pantry without a sense of reasonable dimensions simply steals some corner from the home office ;-)
But that’s exactly what such forums are for, so that everyone can stumble a bit at the beginning when learning to ice skate.