By Emma Thomasson, Sonya Dowsett BERLIN/MADRID (Reuters) – Models testing fashion brands like Adidas ADSGn.DE, Benetton and Gap GPS.N are finding that almost a third of the shoes and clothes they try on are bigger or smaller than the size on the label indicates, explaining why many clothes bought online are sent back. Calculating sizes more accurately could help online retailers like Germany’s Zalando ZALG.DE and Britain’s ASOS ASOS.L cut costly returns and improve customer satisfaction.