If your public IP is IPv6 then it will be shown in IPv6 format. If your public IP is IPv4 then it will be shown in IPv4 format. It's nothing to do with this site. It's about your ISP.
If your public IP is IPv6 then it will be shown in IPv6 format. If your public IP is IPv4 then it will be shown in IPv4 format. It's nothing to do with this site. It's about your ISP.