The side rooms were arranged one above another in three levels of thirty rooms each. There were ledges all around the wall of the temple to serve as supports for the side rooms, so that the supports would not be fastened into the wall of the temple itself.
KJV
And the side chambers [were] three, one over another, and thirty in order; and they entered into the wall which [was] of the house for the side chambers round about, that they might have hold, but they had not hold in the wall of the house.
ASV
And the side-chambers were in three stories, one over another, and thirty in order; and they entered into the wall which belonged to the house for the side-chambers round about, that they might have hold therein, and not have hold in the wall of the house.