-35.65% is the change from 993 to 639
Calculation steps:
[( 639 - 993 ) ÷ 993] x 100 = -35.65%
Formula
Percentage change = [(639 - 993) / 993] x 100
Subtract the new number by the original number
639 - 993 = -354
-354 ÷ 993 = -0.3564954682779456
-0.3564954682779456 x 100 = -35.65%