64.06% is the change from 512 to 840
Calculation steps:
[( 840 - 512 ) ÷ 512] x 100 = 64.06%
Formula
Percentage change = [(840 - 512) / 512] x 100
Subtract the new number by the original number
840 - 512 = 328
328 ÷ 512 = 0.640625
0.640625 x 100 = 64.06%