We do not display spread trades on the chart. The opening price we display on the quote board is reported to us by the exchange and will be whatever the first trade is regardless or type. So if the first trade registered is a spread trade the chart will not pick it up.
Remember that since spread trades are not displayed on the charts, other things may be slightly off such as volumes. This is generally fine because the main goal of the chart is to determine trends in market, and the data we show is the best for that purpose.