maybe i am confused..
"copying formulas for the store comparison figure."

let's say your store values are on A1:A10 [a total of 10 store]

if i want to compare store values of a same product.

1. on B1=A1/sum($A$1:$A$10) [click %]
hence each store will have a % of the total store
summing it to a total store equal to 100%.
this is the way i guess for comparing each store.

2. comparing the store with the MEAN average of all store
on C1=A1/AVERAGE($A$1:$A$10) [click %]

happy holidays