In the active (purchased) version of the app, there are no restrictions on file size downloads. You can download files of any size without limitations.
However, during the trial period, there is a file size download limit of 15 MB. This means you can only download files that are 15 MB or smaller until you purchase the app. Once you have an active license, which is issued after payment, the file size limit is completely removed. You will then have unrestricted access to download files of any size.