The PHP configuration for uploading files via PHP is generally limited to 16MB per upload instance which happens only if you try to upload via HTTP form more than 16mb file.
This setting has been limited in size because if not limited then a misc user can upload huge amount of “temporary” files and fill in the hard drive with spam thus crash the server.
If you need this limit increased you can safely do so by changing the PHP Variable for “upload_max_filesize” in the CPanel-> “PHP Variables Manager”
You can safely set it from 16mb up to 200mb.
If you are not familiar with CPanel File Manager please check out this tutorial here.