[Koha] Koha delete Item type

Hi Koha Team, After installing Koha 3.20 on Ubuntu 14.04 and setting up libraries and items type and other necessary customization of modules, I did a mistake on Item type which I would like to delete one of the Item type. I found the mistake after doing a catalogue test to one of the item and I wanted to delete the item type but I could not. I got the message saying; cannot delete item type. The record is used 1 times. Deletion is not possible. Can someone help to advice simple way to delete the item type or has someone have similar issue before that advice. Thanks and appreciate any feedbacks so I can start complete the Koha setup. Decka PNG