The TOP LIMIT of file size is actually set by your server config with php.ini.
For example (see attached screenshot) The Administrators group is saying that it will allow 100M attachments, but the description above says that the php.ini on the server will only allow 20M. So the limit is actually only 20M. The end result of attempting to upload anything beyond the php.ini 20M setting is that nothing gets stored, and you are left with a zero-byte file.
