How to calcualte total for column if I use filter?

I have a table, and I have a filtetration for it Like:

this.api().column(4).search(_some_filtration_).draw();

And I want to get total sum in footer, So I took code from example:

total_util = this.api.column(4).data().reduce( function (a, b) {return a + b}, 0 );
console.log(total_util)

But it will always give me the value without using any filter