Context Transition Issue

In the below image, you can see that there are different results for the Fabrikam brand. 

The following are the dax measures. 

Fabrikam Sales= sumx(

filter(Sales,

Related(Product[Brand])="Fabrikam"
),[Sales Amount)

Contosa Sales= sumx(

filter(Sales,

Related(Product[Brand])="Contoso"
),[Sales Amount)

I know that the above DAX measures are not the correct approach.  but i want to understand the context transitions issues in the above measures.  Datalink Path shared. 

I wanted to know why Fabrikam Sales measure value is not matching with the Fabrikam Sales Amount Value. My doubt is that if there are context transitions issues in Fabrikam Sales then the same is applicable for Contoso brand. How ContosaSales Measure is successful. Why it did not show the difference in values. I want to know the row value of fabrikam Sales that have resulted into difference of values. 

This is required for understanding purposes.