Struggling with Matrix Layout

Hello.  I feel like I'm missing something simple here, but how can I create a visual like the one below, but where the month headers run along the top as columns, and the various metrics titles run down the side as rows?   Whilst the table below does work, I'd rather it was oriented the other way around as I have 40 different metrics to list, and only 12 months (obviously!).  

If I simply move the 'Completion Month' to the Columns box instead, it doesn't display what I need, as all the different items in the 'Values' section end up as columns too.  

Can anyone help, please?  Essentially, I want it to be laid out like this Excel file.  

Many Thanks