It’s unclear how you’ve been editing the CSS for the plugin. The recommended approach is to create a custom CSS file and load it through your theme’s functions.php (see https://www.vicchi.org/codeage/wp-biographia/hacking-wp-biographias-appearance-with-css/).
Overall, the CSS changes you’ll need to make will depend on your theme. You’ll probably need to reduce the bottom padding for the wp-biographia-container-top div; the default version the plugin ships with has 20px padding on all sides. If this doesn’t reduce the whitespace sufficiently for your needs you can also reduce the bottom margin for the same div; again, the plugin ships with a default of 20px margin on all sides.
Something like the following combines both of these changes; though you’ll probably need to tweak this a bit for your site’s needs …
.wp-biographia-container-top {
margin: 20px 20px 0 20px;
padding: 20px 20px 0 20px;
}
-Gary
