-19.87% is the change from 639 to 512
Calculation steps:
[( 512 - 639 ) ÷ 639] x 100 = -19.87%
Formula
Percentage change = [(512 - 639) / 639] x 100
Subtract the new number by the original number
512 - 639 = -127
-127 ÷ 639 = -0.19874804381846636
-0.19874804381846636 x 100 = -19.87%