It could be spam ?

May be this helps also: Options > Downloads:Enable or disable logging for downloads, uploads or both. Be aware, logging of downloads and uploads can take a lot of memory in case a lot of downloads or uploads is done on your site. It is recommended to enable it only for short testing period
https://www.phoca.cz/documents/17-phoca-down ... e-joomla-3Set maximum count of files user can download. Be aware, 0 (Zero) means, there is no limit. It is limit per file NOT for all downloads. If you set some limit here, anonymous users (guests) are not able to download any file.
Make an update please to version 3.1.0I have the verisone 3.0.6