View this artwork by appointment, at Tate Britain's Prints and Drawings Rooms
There are two diagrams here, each of which comprises a horizontal rectangle with various internal divisions. The upper one may be a ground plan of a domestic building, with pairs of short strokes bisecting the lines at each end marking windows or doorways. Those measurements directly below the main divisions add up to 47, presumably indicating feet (about 14 metres).
The diagram in the centre of the page is divided into three adjoining squares, the outer two being filled with upper and lower bands of vertical hatching, with further details including diagonal lines in the right-hand square. The overall long dimension of this structure is presumably 33 feet (10 metres).