Upgrade- Boot location Install Configuration to Yes or No.

No, it's not always necessary. For example, if you just created a new boot location then this new boot location will hold a configuration that is recent and up-to-date, so there's no need to install the configuration. But if this boot location was created a week ago, then the current configuration may has changes that are not in the configuration of the boot location that was created a week ago. In this case you may want to install the configuration again.