Laminated floor expansion - How do you install under seat?

I read somwhere that it is the subfloor that moves, this would be why you need some expansion space. Perfo itself is, I think, pretty stable stuff.

When I installed the hardwood floor in the house, I nailed it down, still I needed to have some space for expansion, so the whole thing needs expansion, floor and subfloor has an assembly. I tried to find what exactly is the expansion needed per square foot, could not find it anywhere on the web.