Delete Books

Hi there,

i really like this plugin, but now i have one problem.
I had 2 Widgets (1 eBook and 1 Kindle), then i deleted the Kindle Widget, because i want the eBook with the pages.
Now i have 2 same Books at the Dashboard, but i can´t delete one of them. The Widget is already deleted, but at the Dashboard it is still there.
How can i delete books at the dashboard widget?

https://wordpress.org/plugins/progressbar-edition-for-readers/