-18.62% is the change from 639 to 520
Calculation steps:
[( 520 - 639 ) ÷ 639] x 100 = -18.62%
Formula
Percentage change = [(520 - 639) / 639] x 100
Subtract the new number by the original number
520 - 639 = -119
-119 ÷ 639 = -0.18622848200312989
-0.18622848200312989 x 100 = -18.62%