If you use thousands and millions in one diagram, check this out.
yAxis: { labels: { formatter: function () { if (this.value.toFixed(0) >= 1000000) { return '$' + this.value.toFixed(0) / 1000000 + 'M'; } else { return '$' + this.value.toFixed(0) / 1000 + 'K'; } } }, title: { text: '' } },
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