What is the difference between my IPv6 /64 "assigned" space and /48 "allocated" space?
Your account will come with a /48 IPv6 block reserved (allocated) for you. However, only the first /64 is active on your VLAN.
The rationale for this is as follows.
As you grow, you may require the entire /48. In the beginning, though, a /64 is sufficient for practically everyone. Assigning more than 264 IP addresses on the same VLAN is simply wasteful.
Customers that have several hosts or services (some VPS', dedicated servers, etc...) may actually have a need to subnet the /48 into several /64's and assign those as they see fit. For those customers, we will route the entire /48 block over a link-local address (fe80::/64). This is standard practice (RFC 3177, RFC 5375).
Please note, however, that this is an experts only option. That is, we assume you know how to set up your side. We will not provide additional support for your end of the link; rather, we will revert it back to the default /64 setup if you can't get it working.
If having the entire /48 routed to your services over a link-local address is still desired, please contact our support staff.