Why Does Reflectance of Floor Surface Change When Making a Cutout between floors?

Hello DIAL,

When I make a cutout between floors in order to make a double-height space, the reflectance of the floor surface (on the 2nd floor) changes without my intension.

I would like to keep it 10 %. It shows 11.6％ here.
If I type the 10% in the box, reflectance of the ceiling surface on the 1st floor changes instead.

What I want is "Ceilings 70％, Walls 50％, Floors 10％" for both 1st and 2nd floor.
Is there a way to do so??

Thank you.

Yo