How to use meter charts?

[Edzzio]

Hello,

First off I'd like to state that I'm a complete beginner when it comes to BIRT. I have a few simple questions to ask:

1. How do you use meter charts in BIRT?
2. What is a category definition? And do I need to define it,?
   In my case I only want to display the maximum value of a column according to another maximum value of another column.

I might have issues explaining myself correctly, so here is, with an image, what I want to make:

I thank you sincerely in advance, and I wish you all a wonderful day.