By default, HighWayPro creates a new short URL for every post you create since the plugin was installed. HighWayPro will also create a new URL when you edit an existing post that doesn’t have a short URL. You can control the type of URL that gets automatically created (or disable the feature altogether) by going to the Preferences tab > URLs.
By default, a unique, 6-number path is generated. If you want the path to consist of letters only you can do so by selecting “alphabetical” from the “Auto generated path type” setting.
The changes will apply to new URLs, existing URLs that were automatically generated will remain untouched.