-49.3% is the change from 639 to 324
Calculation steps:
[( 324 - 639 ) ÷ 639] x 100 = -49.3%
Formula
Percentage change = [(324 - 639) / 639] x 100
Subtract the new number by the original number
324 - 639 = -315
-315 ÷ 639 = -0.49295774647887325
-0.49295774647887325 x 100 = -49.3%