-83.9% is the change from 621 to 100
Calculation steps:
[( 100 - 621 ) ÷ 621] x 100 = -83.9%
Formula
Percentage change = [(100 - 621) / 621] x 100
Subtract the new number by the original number
100 - 621 = -521
-521 ÷ 621 = -0.8389694041867954
-0.8389694041867954 x 100 = -83.9%