I have a question with 621 options in a drop down but after 260 I get an error -
(Not all answer options were saved. This usually happens due to server limitations ( PHP setting max_input_vars) - please contact your system administrator.)
Depending on your webserver/php setup you need to change the values in the php.ini.
There might be other ways (e.g. apache via htaccess) do modify the php variables. But that can be only answered by someone who setup the webserver/php combo.
php.net/manual/en/info.configuration.php#ini.max-input-vars