How to edit cluster map, add some text to the markers

[mjlsnombrado]

Hi all,

I want to edit cluster map markers and add some text to it, the text will be dynamic depending on what city it is placed, I will need to use javascript/script but I don't know what attribute is needed to be modified below are the sample screenshot of the actual map and the final output

Your suggestions is very much appreciated, thanks in advance.

Actual result :

Expected output :

[kmm2]

I am looking to add text as well.   I am trying to add tooltip string but havent had any luck.