Starting from 8 May 2015 all reports are updated automatically. Therefore,the feature is no longer available and this article is outdated.
Using this feature your form visitors can update the report after new submissions have been made.
To enable this feature you need to create a custom report, as the default report is always updated automatically. Here are the steps for enabling the Update Report button:
As the form owner, you can use the Update Report button from the Reports section at any time, but other users can’t use it more than one time during an hour, in order for the feature not to be abused. If, after one hour, the button doesn’t appear on your public report, it’s because another user has already used it.
Important: If you’ve set your form to redirect the user to the report after submission (Form Owner Options → Thank You Page and Redirects), the feature is no longer available, because the report is automatically updated after each submission. The Update Report link shows only when the custom report is accessed directly from your website or from its direct link.