I am implementing the moving average filter in Matlab. Using fvtool on this filter, gave the following output curve, is this group delay curve correct?

I am implementing the moving average filter in Matlab. Using fvtool on this filter, gave the following output curve, is this group delay curve correct?

Edit:

1. My confusion is regarding the values of the delay output as well as the constant nature of the curve.

I implemented the filter using 'FilterDesigner' tool in matlab (In which, filter dimensions can be specified in the GUI, which then handles the code itself) Attaching a screenshot of the tool window with filter parameters.

After which I exported this filter as an object called 'Hd'

To plot the filter, I did -

fvtool(Hd) 

Which resulted in the curve above (figure 1)