Setting float:left to the original input makes it carry over to the input used inside the NumericTextBox (the widget wrapper contains an input and a couple of other elements – the spinner wrapper and the spinner elements, as well as a second, hidden input). With float:left it looks exactly like the original widget in Chrome and Edge.
If you want to float the widget itself, you can use something like the following CSS:
You can see it in action here: http://dojo.telerik.com/eWiVE/5
If this is not what you need, please clarify your use case, and we will do our best to help you achieve it.