TradeStation Help
When you apply an indicator to a multi-data chart, by default it is based on the base price data you applied to the chart, referred to as Data1. However, you can choose to base the indicator on any of the other symbols in the chart.
The symbols and indicators will still be plotted in the same subgraphs as they were prior to this modification; however, the indicator will now be calculated based on the symbol that you selected.