DAX Subtract Pivot Table Columns Measure

I am relatively new to DAX and I am stuck at one point where I am trying to calculate the difference between two dates.

For example, the current setup of the table looks like this:

The 1 that we can is coming from a measure that I have created

CALCULATE([Total_Red_count],FILTER('Coles Data','Coles Data'[FW_END_DATE_MAX]=FIRSTNONBLANK('Coles Data'[FiscalWeekEndDate],'Coles Data'[FiscalWeekEndDate])))
return result

Now, the next step that I can't seem to figure out is how should I subtract those columns within DAX. For instance, how should I go about subtracting 2/08/2020 from 28/06/2020. The answer should be 0. I need to do this across the entire table and then aggregate this by -1 and 1. -1 means the product was removed and 1 would be that the product was added. Happy to post more examples if you require.

Can anyone please assist with this?

Thank you