Matrix Sub row totals

Hey everyone!

I have a problem in my matrix that i think you might be able to help me out!

I got a matrix with an instalation and in everyone theres a dropdown with the first 3 years of that instalation. And every year i want to get the initial date and the end date. I got to that part and is working fine, but the probçem is that in the matrix the sub row totals are always getting the highest date, so in one column "Final date" its okay but on the initial date im getting the last first date and not the "first first" date.

Can anyone help me with this? Hopefully i explained it properly.

Thanks in advance