-20.38% is the change from 800 to 637
Calculation steps:
[( 637 - 800 ) ÷ 800] x 100 = -20.38%
Formula
Percentage change = [(637 - 800) / 800] x 100
Subtract the new number by the original number
637 - 800 = -163
-163 ÷ 800 = -0.20375
-0.20375 x 100 = -20.38%