How do I constrain a timechart's x-axis range, but still predict on more values than are displayed?

Hello, Using Splunk Enterprise 6.2 I am running a prediction using 30+ historical days of data to predict the next 24 hours of a week day of a particular transaction's volume. When creating the timechart, I do not want to show all 30+ days of data, but I still want to leverage that data in the prediction for the next 24-hour period. I need to limit the displayed time range to something like `earliest=-48` and `latest=+24h`, constantly rolling around the time period of "now". I am not having any luck with XML edits, such as "charting.axisX.minimumTime"/"charting.axisX.maximumTime". Thanks, -J