海图-绘制折线图与汇总值，但显示分手悬停

I am using Highcharts - Line - Ajax. Let's say I have two series of data - 'Headcount 1' and 'Headcount 2'. I want to draw a line graph of 'Headcount', which is the sum of the 2 series. However, when someone hovers on one data point, I want to show the individual values in the callout. Is this possible? How can I do this?I am using Highcharts - Line - Ajax. Let's say