How to open budget allocation & structure planning Doc?

Hi Gurus,

I need to understand where exactly a particular Minus in IM Program comes from. So I see a minus in IM32:

I Open Line items for it & gives me a document number:

I click on F1 for the doc Number and see that its is:

Document number from budget allocation & structure planning

But I cant find in which transaction I can open that Document, so that I can follow how exactly those -70 were calculated or where thay came from...

Many thanks in advance