Homme Plisse Issey Miyake Pants Sizing

Hello all! I'm trying to purchase a pair of Issey Miyake Homme Plisse pants, but I am unfortunately confused by the sizing, with the 1 - 4. I understand that the sizing is based on height, but (and I am probably overthinking here) is it the sizing of the pant or the sizing of the wearer? Most of the videos I have seen don't clearly say how the sizing works and what to be looking for, and most of the people making the videos aren't my size, 5'10, 177 - 178cm, and an athletic build. I would appreciate any tips and suggestions, and pointings in the right direction. Thank you!