If you have MinValue = -56 and MaxValue = 50, that means that your range is 106 (=2x53). You need to choose 1 or 2 for step in order to have the 0 value displayed on your axis.
Another option is to choose your step value depending on the minimum. For example you can choose Step = 14. But in that case you won't have the maximum value displayed with label.
the Telerik team