99.69% is the change from 320 to 639
Calculation steps:
[( 639 - 320 ) ÷ 320] x 100 = 99.69%
Formula
Percentage change = [(639 - 320) / 320] x 100
Subtract the new number by the original number
639 - 320 = 319
319 ÷ 320 = 0.996875
0.996875 x 100 = 99.69%