Google Reader API not showing all results

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I'm using Google reader API to get all available items for any RSS feed. I use it as follows:

http://www.google.com/reader/atom/feed/[RSS FEED LINK]?n=[NUMBER OF ITEMS TO SHOW]&r=o&ot=[UNIX TIME STAMP FOR START DATE]

As I understand, this should return all items starting with the date specified by the time stamp (start date should not be older than one month ago). It works great for some feeds, but in most feeds, it doesn't show all available items (although they are available when using Google Reader).

For Example:

http://www.google.com/reader/atom/feed/http://www.360cities.net/rss/area/Greece.rss?n=1000&r=o&ot=1306959543

this link only shows items for 24,25-07-2011 although it should show items starting with 26-06-2011. If the same link (http://www.360cities.net/rss/area/Greece.rss) is read by Google Reader, it'll show much more results.

Have any solutions?