-99.09% is the change from 660 to 6
Calculation steps:
[( 6 - 660 ) ÷ 660] x 100 = -99.09%
Formula
Percentage change = [(6 - 660) / 660] x 100
Subtract the new number by the original number
6 - 660 = -654
-654 ÷ 660 = -0.990909090909091
-0.990909090909091 x 100 = -99.09%