Highcharts Modify Tooltip for One Series - highcharts

Question

Highcharts: I have a shared tooltip with 3 default bullets. I need to add custom information to the 3rd bullet (or series).
I need Bullet C to show its default value, but also show what percentage it is of Bullet B. In the screenshot below, Bullet C would say: "Good Condition: 3,448 (32% of Assessed).
My question is 2 parts:
How do I customize only the third bullet tooltip?
How do I find out what percentage of Bullet B is represented by Bullet C? (in my example, 3,448 is 32% of 10,697, but how do i find that using highcharts?)
Update: This code formats the bullet and partially answers my first question (except it's missing the comma for thousands format):
return '<span style="color:' + this.series.color + '">● </span>' + this.series.name + ':<b>' + this.y + '</b><br/>';

Answer 1

You can define individual tooltip options for a series, in your case you need to use pointFormatter function, for example:
series: [..., {
...,
tooltip: {
pointFormatter: function() {
var series = this.series.chart.series,
percentage = Highcharts.numberFormat(
this.y / series[1].points[this.index].y * 100,
2
);
return '<span style="color:' +
this.color + '">●</span> ' +
this.series.name + ': <b>' +
Highcharts.numberFormat(this.y, 0) +
'</b> Percentage: ' + percentage + '%<br/>'
}
}
}]
Live demo: http://jsfiddle.net/BlackLabel/6m4e8x0y/4955/
API Reference:
https://api.highcharts.com/highcharts/series.column.tooltip
https://api.highcharts.com/class-reference/Highcharts#.numberFormat