Hi p2662m,
The store window is set to display 14 items at a time and is refreshed every 2 hours. When the store window refreshes, it is repopulated with a selection of 14 active listings ending around the same time as the next auction of yours that is viewed. We will be increasing the store window capacity to 20 in the near future.
The only way you can control what goes in your store window is by making items hidden. To do this, go to Auctiva -> Store(tab) -> Edit Items. Items that are made hidden will not be shown in your store window the next time it refreshes.
Basically, the only way to ensure that this particular item is displayed in your store window is to make enough listings hidden that this is one of fewer than 14 listings that are visible in your Auctiva store.
-Mike