-51.17% is the change from 639 to 312
Calculation steps:
[( 312 - 639 ) ÷ 639] x 100 = -51.17%
Formula
Percentage change = [(312 - 639) / 639] x 100
Subtract the new number by the original number
312 - 639 = -327
-327 ÷ 639 = -0.5117370892018779
-0.5117370892018779 x 100 = -51.17%