Yaxis 0 not aligned with x axis

<charts:XYChart Grid.Row="1" GridLineMajorVisibility="Y" GridStripeVisibility="None" Margin="10" IsLegendVisible="True" 
                                LegendHorizontalPosition="RightOutside" 
                                                       LegendVerticalPosition="CenterOutside" >
                    <charts:XYChart.SeriesStyleSelector>

                        <!-- A custom palette is defined by setting colors on SeriesPaletteStyleSelector.Palette -->
                        <charts:SeriesPaletteStyleSelector>
                            <charts:Palette>
                                <Color>Red</Color>
                                <Color>Orange</Color>
                                <Color>Green</Color>
                                <Color>Brown</Color>
                            </charts:Palette>
                        </charts:SeriesPaletteStyleSelector>

                    </charts:XYChart.SeriesStyleSelector>
                    <charts:XYChart.YAxes>
                        <charts:XYDoubleAxis x:Name="y1" TickMajorInterval="4" TickMinorInterval="1" AreMajorTicksVisible="True" Minimum="0.0" AreMinorTicksVisible="True" />
                        <charts:XYDoubleAxis x:Name="y2" AreMajorTicksVisible="True" TickMajorInterval="5" Position="FarEdge" Minimum="0.0" />
                    </charts:XYChart.YAxes>
                    <charts:XYChart.XAxes>
                        <charts:XYDoubleAxis LabelFormat="{}{0:0}" AreLabelsVisible="True"/>
                    </charts:XYChart.XAxes>
                    <charts:BarSeries Description="Open" LabelVisibility="PointerProximity" ItemsSource="{Binding Data30Minutes}"   YPath="Open" StackKind="Normal"  YAxis="{Binding ElementName=y1}" XPath="DigitalFlag"/>
                    <charts:BarSeries Description="In Progress" LabelVisibility="PointerProximity" ItemsSource="{Binding Data30Minutes}" YPath="InProgress" StackKind="Normal"  YAxis="{Binding ElementName=y1}" XPath="DigitalFlag"/>
                    <charts:BarSeries Description="Closed" LabelVisibility="PointerProximity" ItemsSource="{Binding Data30Minutes}" YPath="Closed" StackKind="Normal"  YAxis="{Binding ElementName=y1}" XPath="DigitalFlag"/>
                    <charts:LineSeries Description="Avg. Wait time" MarkerVisibility="All" LabelFormat="{}{0:0.00}" LabelVisibility="Visible" ItemsSource="{Binding Data30Minutes}" YPath="AverageWaitTime" YAxis="{Binding ElementName=y2}" XPath="DigitalFlag"/>
                </charts:XYChart>

 Above is my xaml code.