-87.17% is the change from 639 to 82
Calculation steps:
[( 82 - 639 ) ÷ 639] x 100 = -87.17%
Formula
Percentage change = [(82 - 639) / 639] x 100
Subtract the new number by the original number
82 - 639 = -557
-557 ÷ 639 = -0.8716744913928013
-0.8716744913928013 x 100 = -87.17%