-18.78% is the change from 639 to 519
Calculation steps:
[( 519 - 639 ) ÷ 639] x 100 = -18.78%
Formula
Percentage change = [(519 - 639) / 639] x 100
Subtract the new number by the original number
519 - 639 = -120
-120 ÷ 639 = -0.18779342723004694
-0.18779342723004694 x 100 = -18.78%