-19.88% is the change from 800 to 641
Calculation steps:
[( 641 - 800 ) ÷ 800] x 100 = -19.88%
Formula
Percentage change = [(641 - 800) / 800] x 100
Subtract the new number by the original number
641 - 800 = -159
-159 ÷ 800 = -0.19875
-0.19875 x 100 = -19.88%