-63.1% is the change from 870 to 321
Calculation steps:
[( 321 - 870 ) ÷ 870] x 100 = -63.1%
Formula
Percentage change = [(321 - 870) / 870] x 100
Subtract the new number by the original number
321 - 870 = -549
-549 ÷ 870 = -0.6310344827586207
-0.6310344827586207 x 100 = -63.1%