According to our experience with the Theme Check validation plugin, the best way to reach the right level is to set the Theme name, the theme slug AND the theme folder with the exact same name.
The development version of the Starter Theme uses the name pg_starter for these values and because we deliver a customized version of functions.php and a few other scripts in the final commercial package, we had to “hardcode” the text_domain value in these files.
This situation is absolutely not an issue if you do not plan to submit your custom theme to the WordPress repository BUT if its part of your plans, you will have to manually replace the pg_starter text_domain value with yours (same value as the theme slug/theme name/theme folder) in the following files:
functions.php located at the root of your project folder
functions-breadcrumb.php located in assets>breadcrumbs
breadcrumb.php located in assets>breadcrumbs
You can easily do this with Atom Editor by just replacing ‘pg_starter’ with ‘your_value’ in the files.