how to scroll fixed amount of bar when scrolling the bar chart? (CHARTS SWIFT)

When I first presenting my chart I Write this.
```
chartView.data = data
chartView.setVisibleXRangeMaximum(4)
chartView.moveViewToX(Double(step.count - 5))
```
So It present me perfectly with the last 4 bars.But when I start to scrolling left to right It does not show me the previous 4 bar. Instead of it present me with some remaining bar and some previous bar.So How can I present it with next 4 bar or previous 4 bar according to our `scroll`.