-12.82% is the change from 390 to 340
Calculation steps:
[( 340 - 390 ) ÷ 390] x 100 = -12.82%
Formula
Percentage change = [(340 - 390) / 390] x 100
Subtract the new number by the original number
340 - 390 = -50
-50 ÷ 390 = -0.1282051282051282
-0.1282051282051282 x 100 = -12.82%