Matrix Table Total Issues

Hi all,

looking for some guidance, I have a matrix table visulisation which links two tables. The link seems to work fine.

Table 1 : Dates Function - Week Number and End of Month

Table 2: Imports - Week Number and Sales

I am then showing Sales by End of month. The purpose of this is I want to build in like for like with Sales this time last year but before I get to this point I've realised the Total of my matrix table doesn't match the value of the lines within.

I've read about Sum and SumX but I can't get the outcome I'm expecting.

I've also tried merging the tables using Lookupvalue to create a new column so everything is in one place.

Visualisation below for reference purposes. Anyone able to advise? 

Thanks in advance.

Regards,

Chris