Bid / Ask Election Prices

How are these prices calculated? http://www.intrade.com/jsp/intrade/intradeTV/liveChart.jsp?dem_id=416542&rep_id=416543&state=INDIANA I am looking at Indiana (link above). Sometimes the prices go out of the Bid / Ask range, or are at the top / bottom of the spread. ie. right now Obama’s price is 69.0 with a 70.0 Bid and 70.1 Ask. Any idea? Maybe it is just a timing delay or something.