Pistons specs question for 340 build

I just had a look at the KB pistons site (they are made by UEM) and their protocol is opposite to what people are talking about here and what I thought would be correct. See the three pictures as well as the link below if interested, you can clearly see that the domed pistons are given as a -ve value and the dished and valve relief pistons are +ve value.

KB AUTOMOTIVE - KB Automotive Hyper

KB Pistons 1.jpg

KB Pistons 2.jpg

KB Pistons 3 (hemi).jpg