-50.55% is the change from 637 to 315
Calculation steps:
[( 315 - 637 ) ÷ 637] x 100 = -50.55%
Formula
Percentage change = [(315 - 637) / 637] x 100
Subtract the new number by the original number
315 - 637 = -322
-322 ÷ 637 = -0.5054945054945055
-0.5054945054945055 x 100 = -50.55%