How does Zoomtovalues Method work?

Problem:
I'm calling the method like this:

zingchart.exec('myid', 'zoomtovalues', {
    xmin: 1235779200000,
    graphid:0,
    xmax: 1238454000000
});

I want to zoom the x axis to cover 28 Feb - 31 Mar (the area shaded in grey in the chart), however, it doesn't work.

Solution:
Use kmin and kmax instead of xmin/xmax and it should work. We've attached the demo for your reference.