-86.4% is the change from 669 to 91
Calculation steps:
[( 91 - 669 ) ÷ 669] x 100 = -86.4%
Formula
Percentage change = [(91 - 669) / 669] x 100
Subtract the new number by the original number
91 - 669 = -578
-578 ÷ 669 = -0.8639760837070254
-0.8639760837070254 x 100 = -86.4%