-98.8% is the change from 666 to 8
Calculation steps:
[( 8 - 666 ) ÷ 666] x 100 = -98.8%
Formula
Percentage change = [(8 - 666) / 666] x 100
Subtract the new number by the original number
8 - 666 = -658
-658 ÷ 666 = -0.987987987987988
-0.987987987987988 x 100 = -98.8%