How to display values above columns in XY Chart?

Tamerplc has a question above

I also need to ask now though, how do I change the font using the technique that Peter suggested

I added a line
I set the stroke opacity 0
I enabled the bullets, set render for label
set text on the label for {valueY}
I adjusted the position with dx and dy by 10 and 10

but my text is large
So I think I want smaller text, and maybe if possible, also round the value

so when I put
text : {valueY}
maybe that is a spot I can put some css to change the font?

Or maybe since I use 8.1.0, there is a way to set this bullet value, not sure how to reference it, but maybe from background I can do it

Then I need to know what the reference is for that text I think

I am not good with css language, but also, I don't know how a person knows the name to call a setting from the property editor