Yeah its not super intuitive. Basically the pieces of furniture that are "tall enough" to block the light from the windows have collision shapes. Raycasts get sent from each grid cell to each window and if they can find a window the cell becomes unlit. As a result, I tried to make the furniture that would block light taller (liked stacked boxes or the taller recliners), and objects that would not block light (like the shoes) shorter. I also tried to rotate them so they would look like they'd block the light, but in reality the rotation of the object didn't make any difference.
Anyway, thank you for playing! :)