Perfect elasticity is where a 1% increase in prices will result in a 1% decrease in demand.
It doesn't actually happen like that. Economics is a social science, not an exact one. PED is a great way of explaining behavior in the market, not predicting them.
If PED were perfectly accurate then a decrease in the price of a good to 0 would result in infinite demand while an increase in the price of a good far beyond its fair value (Say, $10,000 for a pizza) would result in no one buying it, rather than the predicted "very few".
A .7% increase in prices won't necessarily result in a .7% decrease in demand.