phpMyAdmin warning

After installing, activating and saving the settings of this the plugin on a local test site, I get the following warning from phpMyAdmin when selecting the wp_options table:

“Warning: a form on this page has more than 1000 fields. On submission, some of the fields might be ignored, due to PHP’s max_input_vars configuration.”

I also notice that after deactivating and deleting the plugin from the plugins area in the dashboard, all of the plugin’s fields remain in the database.

https://wordpress.org/plugins/optin-forms/