Any way to access Metric value through JSON input field

I am looking to apply a floor() method on the overall average of a field calculated in 'Metric' visualisation in Kibana. I cannot apply floor() on each value in document since it will give incorrect value. Is there a way to access the metric value calculated in JSON input field so that I can apply floor() function to it.
I dont think this will work via scripted fields since I want to apply the method on a whole metric and not one document.

@majagrubic can you help please