Apportioning values on Power BI

Afternoon All,

I am a new to Power BI, so apologies if the below has already been covered in earlier posts.

We have invoice values that we need to apportion royalty payments to. As our products have multiple royalties applicable against them I am looking to calculate an appotioned value per item for each aplicable royalty code, and then calculate the royalty applicable to each item / royalty code combination.

The apportioned values that I have work okay except for grand totals which are sadly incorrect.

Below are headers from two data tables that I am linking for this purpose, is there a failsafe formula that I can use to get correct values throughout my table / matrix ?

Any help / guidance would be much appreciated.