Can somebody explain to me how the ZSS format works for exported subscreens?

I'm trying to edit a Z3-styled subscreen, and just handling the magic meter is a huge pain because there are several dozen pieces which all default to a page waaaaaay down there in the tileset. I had figured editing the exported ZSS directly would be a quick way around that, but there are so many properties for each entry that it's very difficult to understand what's going on.