By default episodes aree listed in reverse date order, i.e. latest on top. You've posted a number of episodes on the same day - since the order would take account of the time of day I wonder whether you posted them out of order, possibly by p[osting them altogether. You can change the order by including an 'itunes episode' tag within the 'item' tags for each episode, reflecting the order you want. In this case it should be the same as the number in the title.
Exactly how you go about doing this depends on how you are making your feed. As O assume you are not hand-writing it you may need to approach the Help for whatever service you are using.