-40.45% is the change from 670 to 399
Calculation steps:
[( 399 - 670 ) ÷ 670] x 100 = -40.45%
Formula
Percentage change = [(399 - 670) / 670] x 100
Subtract the new number by the original number
399 - 670 = -271
-271 ÷ 670 = -0.4044776119402985
-0.4044776119402985 x 100 = -40.45%