Sentence:  The length of the arrow indicates amount of slowing or acceleration at Completion over that at Onset , and the difference in months can be read roughly by referring the arrow to the age scale along the base of each figure , or more precisely by referring to the <WSD>original</WSD> data in the appropriate tables . 
Meaning of the word marked with <WSD> tags:  not derived or copied or translated from something else; not an adaptation"