You've asked this at https://github.com/ag-grid/ag-charts/issues/4606 and I've responded there with an example of https://plnkr.co/edit/KUIMbVpydQabuKTa where manual padding is utilised.

Additionally, I have modified your example to used our unit-time axis and Date objects - see https://www.ag-grid.com/charts/javascript/axes-time/ for more information about this.

As mentioned there, we have a feature request on our backlog for automatic padding.

You can track it on our pipeline with this reference:
AG-8163 - [Charts] Allow automatic series area padding if necessary

Thanks

David