This is a demo tutorial. While there is no step-by-step commentary available (yet), the live demo below is fully functional. Feel free to open it for full source code.
This demo shows how we can make LineSeries show its last value using two approaches: as a label next to bullet, and as an axis range with a label.
Using bullet label
See the Pen amCharts 4: Show last value at the end of LineSeries by amCharts team (@amcharts) on CodePen.
Using axis range
See the Pen amCharts 4: Last value (using AxisRange) by amCharts team (@amcharts) on CodePen.