-17.12% is the change from 771 to 639
Calculation steps:
[( 639 - 771 ) ÷ 771] x 100 = -17.12%
Formula
Percentage change = [(639 - 771) / 771] x 100
Subtract the new number by the original number
639 - 771 = -132
-132 ÷ 771 = -0.17120622568093385
-0.17120622568093385 x 100 = -17.12%