Each VPS includes a dedicated IPv4 address. That address is the one in the
provisioning email and on the instance page.
Floating IPs are additional addresses you order from the client portal and
assign to a server. They bill separately (hourly, like everything else) for
as long as they are reserved, assigned or not.
Release a floating IP you no longer need so it stops charging. Reverse DNS
for both the primary and floating addresses is configured from Reverse DNS
in the portal.