-52.44% is the change from 820 to 390
Calculation steps:
[( 390 - 820 ) ÷ 820] x 100 = -52.44%
Formula
Percentage change = [(390 - 820) / 820] x 100
Subtract the new number by the original number
390 - 820 = -430
-430 ÷ 820 = -0.524390243902439
-0.524390243902439 x 100 = -52.44%