The bottom section of the domain and DNS settings page gives options for how the various DNS records are shown on the DNS page for your domain name. If you've not gotten that far into your account yet, the DNS page is accessed for any given domain by clicking the "dns" link beside the domain name, and gives a list of all the records associated with that domain. For any given record, there are 2 or 3 different ways it can be displayed, and these settings allow you to change from one form to another