Hi, I used to use IboUI for a long time to get these values show on my own, my focus' and my target's health and resource bars: http://i.imgur.com/EhT9Tse.jpg
Since I started crashing while using this addon during raids I can no longer really use this addon since it hasn't been updated for years.
I was looking for a way to maintain this perfect looking health bar. I downloaded Lorti UI and It's the same (graphic wise) EXPECT for the values shown on the health bar. I want 1 absolute number (e.g. just 50k, not 50k/50k) with the percentage next to it (like the screenshot obviously).
Shadowed Unit Frames can display values like that. You can pick any combination of percentage/absolute/fraction/whatever and choose which side and position of the frame to display them.
Well Shadowed Unit Frames has its own custom unit frames (as the name states) but it allows you to choose what text to display on the center of the unit frame,on the left side,on the right side with different values.The same as the example of your picture (eg Current Health on the left Percentage Health on the right) but that makes the addon change the default ones to a box not use the default skin.You could try UnitFramesImproved but I honestly don't know any addon that could do that on its own.
In general addons can't change text that's displayed for unit frames provided by any arbitrary unit frames addon. In these situations, if you're unwilling to switch unit frames, you usually have 2 options:
1. Ask the specific addon's author to implement the functionality you want.
2. Ask the community to create a plugin or code change for the specific addon to implement the functionality you want.