-97.76% is the change from 671 to 15
Calculation steps:
[( 15 - 671 ) ÷ 671] x 100 = -97.76%
Formula
Percentage change = [(15 - 671) / 671] x 100
Subtract the new number by the original number
15 - 671 = -656
-656 ÷ 671 = -0.977645305514158
-0.977645305514158 x 100 = -97.76%