Blended Data - Aggregation / Field Type

Hi everyone, 

I'm blending 2 sources, in a left outer join being the left table:

Product code | Name | Guests

and the right table:

Product code | Expenses

I'm joining the tables by using the key 'Product code' and I want to add up Expenses (Sum, metric).

However, I see that I am also adding guests for every line of expenses that I have in my data source. Example: A product code with 11 guests, and 3 lines of input for expenses, will show up as 33 guests.

Can you tell me what I'm doing wrong? I tried adding 'Guests' as a dimension but the problem is that I want to treat it as a number and obtain a 'Total sum' of guests in the end, so that shouldn't work. Is it a problem with my joins maybe? Thanks!

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