The Milliseconds are missing from ChartAxisLabelsDateFormats and so there is no Milliseconds(string format) in ChartAxisLabelsDateFormatsBuilder.
https://docs.telerik.com/aspnet-mvc/api/kendo.mvc.ui.fluent/chartaxislabelsdateformatsbuilder
This means that to configure it, we have to config it from client js on load.
Here is a REPL sample for your reference: https://netcorerepl.telerik.com/GSbERuaZ56uDsrQ714