3.06% is the change from 620 to 639
Calculation steps:
[( 639 - 620 ) ÷ 620] x 100 = 3.06%
Formula
Percentage change = [(639 - 620) / 620] x 100
Subtract the new number by the original number
639 - 620 = 19
19 ÷ 620 = 0.03064516129032258
0.03064516129032258 x 100 = 3.06%