Put simply the scanner can misread your foot. Without a professional examining and looking at your foot there is a lot of room for mechanical error. My son hopped on it the other day. I was curious so I indulged at watched him. 
 He has a flat foot with some issues in the front of his foot. He has been in out little steps and doing great,  the scanner said he had a high arched foot and that he needed very little support and lots of cushion. It suggested the completely wrong orthtotic. I feel bad when patients come in gap having spent $50 and I get to be the bearer of bad news that it was the wrong insert. 
My suggestion...get a full evaluation by a professional and find out what you really need before letting a machine guess and waste your hard earned money!