Simple dimensioning

Hi,
I just want to be able to create a simple geometry like a rectangle in Hypermesh and then change its dimensions easily with a dimension parameter. I tried this according to the tutorial 'dimensioning' from Hypermesh tutorials. 

Let's take a mere rectangle created using Geometry ->  Surface -> rectangle. When I create a dimension 'height' for one of its edge, the dimension 'height' appears as a feature but not as a parameter which means that I can't change the height of this edge. 

 

 

Please see below the image from the tutorial and note the difference with my example :

 

So, finally, my question is how do use the dimensioning features if I create my own geometry in Hypermesh ? I feel dumb asking this question and you may feel dumb being asked this question, but I proved that it doesn't work like it's supposed to be working. Thank you in advance !

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