Format values interval in facechart

[LeoPc88]

1.SmartClient Version 8.3
2.Google Chrome

Hi, I had create a facetchart and I facing problem with format the Y-axis value by setting its interval. Currently it automatic set the interval value by 10 based on my data, but I wan set interval by 50 for the Y-axis. How to do this? here is my code:

isc.FacetChart.create({
    ID: "YieldAndDefectiveAnalysisByPONumberChart",
    width: "100%",
    height: "100%",
    chartType: "Column",
    stacked: true,
    valueProperty: "percent",
    showValueOnHover: true,
    updateData: function (dynamicCriteria) {
        var self = this;
        YieldAndDefectiveAnalysisByPONumberFetchDS.fetchData(
         dynamicCriteria,
          function (dsResponse, data, dsRequest) {
              self.setData(data);
          }
        );
    },
    facets: [
       {
           id: "MachineName"
       },
       {
           id: "area"
       }
    ],
    showShadows: false,
    border: "1px solid black",
    showTitle: false,
    dataMargin: 200,
    dataColors: ["#fffd53", "#f8c14c", "#60ffff", "#97E997", "#F36050", "#7F62B4"],
    chartBackgroundDrawn: function () {
        var values = this.getFacetData().getProperty(["percent"]);
        var sum = 0;

        for (var i = 0, l = values.length; i < l; i++) {
            sum = sum + parseFloat(values[i]);
        }
        avgLineY = this.getYCoord(sum / l);

        isc.DrawLine.create({
            drawPane: this,
            startPoint: [this.getChartLeft(), avgLineY],
            endPoint: [this.getChartLeft() + this.getChartWidth(), avgLineY],
            autoDraw: true
        }, {
            lineWidth: 4,
            lineColor: "red",
            linePattern: "solid"
        });
    },
    barProperties: {
        click: function () {
            var a = YieldAndDefectiveAnalysisByPONumberChart.getNearestDrawnValue(YieldAndDefectiveAnalysisByPONumberChart.getOffsetX(), YieldAndDefectiveAnalysisByPONumberChart.getOffsetY());
            LoadYieldAnalysisByDay(a.facetValues.MachineName);

        }
    }
});

Hope someone can help, thanks in advanced.