Between the two windows is a large square hole cut into the stone wall, this would have been a Aumbray. Think of it as a moden day chest of drawers and this being one of the drawers to store items. This cupboard would have had a lockable door.
On the opposite side next to the entrance door and toilet there is another inset into the stone work, it is just as not as deep in depth but is larger in width and height. It has certainly been cut out in more recent times and supposition is that blocks may have been emoved during the early 20th century refurbishment of the castle and the stone used elsewhere.
The two large wall recesses seem to be unique to this castle and similar is not seen anywhere else in castles throughout the area so the notion they were cut out and reused is not far from reality.