This value is not set by the BBIS application, but instead comes from the document's title, which is found in the file's properties. Where the title field is located in the file properties is dependent upon the file type and program used to open the file. Below are a few examples.

In Microsoft Word, click File > Info. On the right side of the window, the section below is displayed.

Word document titlefield

In Adobe Acrobat, click File > Properties > Description tab. The title field is at the top of the form as seen in the screenshot below.

Title field in PDF