-99.1% is the change from 670 to 6
Calculation steps:
[( 6 - 670 ) ÷ 670] x 100 = -99.1%
Formula
Percentage change = [(6 - 670) / 670] x 100
Subtract the new number by the original number
6 - 670 = -664
-664 ÷ 670 = -0.991044776119403
-0.991044776119403 x 100 = -99.1%