-60.09% is the change from 639 to 255
Calculation steps:
[( 255 - 639 ) ÷ 639] x 100 = -60.09%
Formula
Percentage change = [(255 - 639) / 639] x 100
Subtract the new number by the original number
255 - 639 = -384
-384 ÷ 639 = -0.6009389671361502
-0.6009389671361502 x 100 = -60.09%