When using numeric text box with AngularJS - the model value should be affected by using the arrows, just like it's affected by typing inside the control.
A model value change for the numeric input is triggered on focus blur, as visible in this example: http://demos.telerik.com/kendo-ui/numerictextbox/angular This behavior is by design, and when you use the arrows of the input the model value will again be updated on blur.