-18.72% is the change from 641 to 521
Calculation steps:
[( 521 - 641 ) ÷ 641] x 100 = -18.72%
Formula
Percentage change = [(521 - 641) / 641] x 100
Subtract the new number by the original number
521 - 641 = -120
-120 ÷ 641 = -0.187207488299532
-0.187207488299532 x 100 = -18.72%