As per Proclarity functionality, Grand total and subtotal functions don’t add value of two measures on different customers or Products.Instead it adds a measures value for different time, product, customer etc. (Grand total don’t add two measures as you can see in the screen below from Adventure works example)
If you want to add these two measures, you need to make a calculated measures. The steps for the same is shown below:
4. Change the name of the measure if needed. Click finish.
5. Now you can use this measure which gives you the summation of two measures.
Keep looking this space for more details on Gran Total functionality and many more....
Till then bbye...