-86.3% is the change from 664 to 91
Calculation steps:
[( 91 - 664 ) ÷ 664] x 100 = -86.3%
Formula
Percentage change = [(91 - 664) / 664] x 100
Subtract the new number by the original number
91 - 664 = -573
-573 ÷ 664 = -0.8629518072289156
-0.8629518072289156 x 100 = -86.3%