The addresses seem to be all even, so I wonder if you meant 5390 (rather than 5309) - it is also listed for 414,900.
There are two sales that are in the listing service at 319K and 369K last quarter of 2007.
There are no properties showing as pending or under contract at this time.
It appears that the builder has listed each property, often on new construction (like cars) list some of the properties and when you get there, there are more options.
An on-site agent would be representing the builder and I would strongly advise you to use a buyer's agent if you don't already have one. It won't cost you anything and they can help you navigate a new construction purchase - which can be complicated.
Also, you should check out the builder's history. Also find out if there is a second phase or anything like that. Buying too early in new construction can put you as one of a few sold and the rest of the lots could be foreclosed on if the builder is in trouble - leaving you in a really bad spot.
I'm, honestly not familiar with the builder - Ross Mundy Custom Homes, but a quick Google of them got me their website, which wasn't working, an article citing two homeowners (probably the two sold last year) and a blog that was just stock messages - none from actual buyers in the subdivision.
I would be sure to do a lot of diligence before you decide to purchase there.
Best of luck to you!