Technically it is a chart and not a graph. A chart maintains history allowing you to send data a point at a time. A graph does not maintain a history.
Use a bundle cluster function to combine the two data points then send to the chart.
Turn on context Help and hover over the terminal for the chart in the block diagram. It will describe how you have to build the data together for different chart scenarios. Same situation if you were working with other types of charts or graphs.
