-37.98% is the change from 840 to 521
Calculation steps:
[( 521 - 840 ) ÷ 840] x 100 = -37.98%
Formula
Percentage change = [(521 - 840) / 840] x 100
Subtract the new number by the original number
521 - 840 = -319
-319 ÷ 840 = -0.37976190476190474
-0.37976190476190474 x 100 = -37.98%