Why were the results of the mimicry study presented as the percent of attacks on king snakes in each area rather than the total number of attacks?

The mimicry study was presented as a percent of attacks in each area because the number of attacks varied between location. The kingsnake was attacked less in the areas where the kingsnake and coral snake overlapped because predators knew to stay away from snakes with that coloration. "The data fit the key prediction of the mimicry hypothesis. Compared to the brown artificial snakes, the ringed artificial snakes were attacked by predators less frequently only in field sites within the geographic range of the poisionous coral snakes." AP edition Biology, eighth edition. Chapter 1 (page 21).