So yes blending is a very particular type of 'Join' (used in the loosest sense!). Here's a blog I wrote on how it works (and when/how to use it)
So any field you bring in, from a secondary source, has to come in as an aggregate. But by defining the blend fields, you can control this.
So the reason you are getting 2088 is that you only have a blend on name...so tableau creates a table (this is just a mental way of thinking about it) at that level, as per the below
An then left joins this table to the primary source, on the name...which is why we get 2088.
Actually what you want to do is create the following aggregate table
and then left Join it back on Name and Month
Had the month field been called the same, as with name, Tableau would have picked this up, but not to fear we can manually create the relationship, using the 'Edit Relationships' in the data menu
Once we have this I create the calc for %age as follows
I then bring this field in...and ensure I click the blend field on Month too
Hope that makes sense, and does what you need.
Blended Calculations.twbx 63.3 KB
Thank you so much for your help! I was able to follow your instructions clearly and it worked! You saved me!!!