-50% is the change from 612 to 306
Calculation steps:
[( 306 - 612 ) ÷ 612] x 100 = -50%
Formula
Percentage change = [(306 - 612) / 612] x 100
Subtract the new number by the original number
306 - 612 = -306
-306 ÷ 612 = -0.5
-0.5 x 100 = -50%
Example