Once a project is deleted, there may be some Project Quotes which is not deleted.  

To delete the “Project Quote” documents:

1.On the Action ribbon, select Edit → Delete

2.Select Documents.

projects-delete-project-quote-menu

3.Select the document type “All”. 

projects-delete-project-quote

4.Click the Delete button. A confirmation message will be displayed:

“Do you want to delete?” will be displayed.

5.Click on the Yes button.