DataGridTemplateColumn Two way binding is not working

public List<Brand> BrandList { get;set;}

<wpfUtilities:BindingProxy x:Key="proxy" Data="{Binding}" />

<DataGridTemplateColumn 
    Header="{Binding Data.TimeColumnHeaderText, Source={StaticResource proxy}}" 
    Width="Auto" 
    IsReadOnly="True"
    >

public class ZlsRouteEditorDataTemplateSelector : DataTemplateSelector
{
    public DataTemplate ViewDataTemplate { get;set; }
    public DataTemplate EditDataTemplate { get; set; }

    public override DataTemplate SelectTemplate(object item, DependencyObject container)
    {
        if (item is ERouteEditor e)
            return _GetTemplate(e);

        ZlsRouteEditor parent = container.TryFindParent<ZlsRouteEditor>();
        if (parent != null)
            return _GetTemplate(parent.Mode);

        return base.SelectTemplate(item, container);
    }

    private DataTemplate _GetTemplate(ERouteEditor e)
    {
        switch (e)
        {
            case ERouteEditor.View:
                return ViewDataTemplate;
            case ERouteEditor.Edit:
                return EditDataTemplate;
            default:
                throw new ArgumentOutOfRangeException();
        }
    }
}

/// <summary>
/// Finds a parent of a given item on the visual tree.
/// </summary>
/// <typeparam name="T">The type of the queried item.</typeparam>
/// <param name="child">A direct or indirect child of the
/// queried item.</param>
/// <returns>The first parent item that matches the submitted
/// type parameter. If not matching item can be found, a null
/// reference is being returned.</returns>
public static T TryFindParent<T>(this DependencyObject child) where T : DependencyObject
{
    //get parent item
    DependencyObject parentObject = GetParentObject(child);

    //we've reached the end of the tree
    if (parentObject == null) return null;

    //check if the parent matches the type we're looking for
    T parent = parentObject as T;
    if (parent != null)
    {
        return parent;
    }
    else
    {
        //use recursion to proceed with next level
        return TryFindParent<T>(parentObject);
    }
}

<DataGridTemplateColumn Header="Station &amp; Programm" Width="*" CellTemplateSelector="{StaticResource StationProgramTemplateSelector}"/>

<StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
    <recipeControls:ZlsRouteEditor Height="570" Margin="5" Mode="View"/>
    <recipeControls:ZlsRouteEditor Height="570" Margin="5" Mode="Edit"/>
</StackPanel>

public int PercentFull { get; set;}
PercentFull = (Convert.ToInt32(c.Quantity) / Convert.ToInt32(data.Capacity) * 100);

public double PercentFull {get; set;}
PercentFull = c.Quantity / Convert.ToDouble(data.Capacity) * 100;

public int PercentFull {get; set;}
PercentFull = Convert.ToInt32(c.Quantity) * 100 / Convert.ToInt32(data.Capacity);