I'm guessing because you must be 8000+ on the list given your take up date. If everyone else before you takes a seat it's unlikely you'll get a none premium seat.
From the sound of other supporters experiences with the sales staff we might find it difficult to shift premium seats until we run out of other seats to sell. Then it depends on if people can afford it or elect to wait until next year to chance their arm on availability then. I doubt you can elect to purchase a premium seat before your allotted time to circumvent the queue.
My new number is 1900ish (from 2200) and I get to choose on 27/05/2015.
Annoying can't see availability until then though to start to weigh options up but seems we get a choice of anywhere available in the stadium!