Now, there is a "Advanced Options" below the 'Theme Name' 'generate' button. Click on Advanced Options for advanced settings. 

The first option is for your theme name. Put your theme name here. The second input field is for your Theme Slug or theme url. Give your theme url here from where user can preview/download or purchase your theme.

Next option is for Author or theme maker. Fill this with your name. And then give your website url.

The last input filed is for description. Fill it with all the details of your theme.

There is also two more extra option for WooCommerce boilerplate and _sassify! Check this if you need this.

After you are done just click on generate. Within a few moments your starter theme will be generated with all necessary and some unnecessary(to me) files. Delete those extra files which you don't need. 

By following this method, you can save your few precious time.