Each number in the first column, labeled , is the number of degrees of arc on a circle. Each number in the second column, labeled , is the length of the corresponding chord of the circle, when the diameter is 120. Thus πδ represents an 84° arc, and the ∠′ after it means one-half, so that πδ∠′ means °. In the next column we see π μα γ, meaning 80 +  + . That is the length of the chord corresponding to an arc of ° when the diameter of the circle is 120. The next column, labeled , for "sixtieths", is the number to be added to the chord length for each 1° increase in the arc, over the span of the next 12°. Thus that last column was used for linear interpolation.