Historic orders are automatically imported and archived by Shopify. The way that the merchant dashboards work on Shopify's end of things, is that archived orders don't get counted in your order total. Archived orders are considered "completed" and thus removed from the order count. The order count that shows in the admin are considered open orders that require attention.So if you go into your archived orders and unarchive them, they will again show up on your dashboard totals.