-99.4% is the change from 670 to 4
Calculation steps:
[( 4 - 670 ) ÷ 670] x 100 = -99.4%
Formula
Percentage change = [(4 - 670) / 670] x 100
Subtract the new number by the original number
4 - 670 = -666
-666 ÷ 670 = -0.9940298507462687
-0.9940298507462687 x 100 = -99.4%