This plugin throws 11 separate "Undefined Index" errors when viewing wp-admin/widgets.php (regardless of whether the widget is active or inactive). The issue seems to be in the function form ($instance) section, where you're calling variables that won't be set until the widget is moved into a widget area and set up. They'll need set similar to how you have $title, $number, and so on set inside function form().
This is a great plugin, and I'll be fixing it up to use on a production site, but in development I run with WP_DEBUG set to TRUE and I hate seeing my logs fill up with errors or notices. Additionally, there's nearly 200 extraneous empty lines that don't denote actual breaks in the code, which makes it a lot more difficult to go through and modify.