-83.08% is the change from 390 to 66
Calculation steps:
[( 66 - 390 ) ÷ 390] x 100 = -83.08%
Formula
Percentage change = [(66 - 390) / 390] x 100
Subtract the new number by the original number
66 - 390 = -324
-324 ÷ 390 = -0.8307692307692308
-0.8307692307692308 x 100 = -83.08%