U.S. online shoppers spent more than $26.4 billion during June 23 to June 26, Adobe Analytics said Numerator said average Prime Day order size fell to $47.66 from $53.34 Adobe said discounts matched last year's levels, suggesting promotions may stay heavy into holidays NEW YORK, (Reuters) - U.S. online shoppers clawed for deals on electronics, appliances, items for children and everyday essentials during Amazon.com's annual sales event Prime Day, spending more than $26.4 billion from June 23...