UBB.threads PHP Forum Software Community Forums UBB.threads 7 Bug Reports Error Messages - What to do???

I am receiving the following WARNING in Admin CP and wondering how to fix that:

WARNING: Your PHP max_input_vars setting is set to a low value. Your current setting is 1000; the default setting is 1000. Based on your current number of forums, a minimum setting of 3540 is recommended. Your forum may have issues such as a blank configuration file, missing settings, or unexpected script behavior if you continue. Please see the "Issues with the PHP 'max_input_vars' Setting" entry on the UBBWiki for more information.