-6.21% is the change from 821 to 770
Calculation steps:
[( 770 - 821 ) ÷ 821] x 100 = -6.21%
Formula
Percentage change = [(770 - 821) / 821] x 100
Subtract the new number by the original number
770 - 821 = -51
-51 ÷ 821 = -0.06211936662606577
-0.06211936662606577 x 100 = -6.21%