I think you can only add labels on a line chart so to do it on your bar chart I think you'll need to duplicate each of the series as a line render and in each of those series set,
line.appearance.bullets.0.enabled : true
line.appearance.bullets.0.render : label
line.appearance.bullets.0.label.text : {valueY}
line.appearance.bullets.0.label.position.dx : <adjust offset here>
line.appearance.bullets.0.label.position.dy : <adjust offset here>
When you have all that working then,
line.appearance.stroke.width : 0
to hide the line and to hide the series label,
hiddenInLegend : false
There was a long discussion here.