-19.09% is the change from 639 to 517
Calculation steps:
[( 517 - 639 ) ÷ 639] x 100 = -19.09%
Formula
Percentage change = [(517 - 639) / 639] x 100
Subtract the new number by the original number
517 - 639 = -122
-122 ÷ 639 = -0.19092331768388107
-0.19092331768388107 x 100 = -19.09%