Eight and twenty cubits. This is the exact length required for a rectangular tented roof over such a space, which should descend (as tent roofs usually do) within about seven feet of the ground. The comparison made in Exodus 26:12, Exodus 26:13, between the fine linen covering of the mishkan and the goats' hair covering of the "tent," implies that the one was directly under the other, and that both were arranged in the same way.
The breadth of four cubits. This gives for the entire length of the curtain (4 by 10), 40 cubits, or ten cubits more than the length of the boarded space. The roof must thus have been advanced some distance in front of the tabernacle proper, or rectangular boarded space.
Every one of the curtains shall have one measure. They shall all, i.e; have the same measure.