Confusion About Search And Filters

OK I've got a search and a filter set up but I'm very confused about filters -

What I want is to give the user filters for dimensions and price. If I go to the "filters" area, I can add a price slider and a something called "size". So ok, there are my two filters. Both are set for global, no specific categories.

When I go to my categories layout manager, if I add the filter block and set it to display both of those filters, only the price filter actually shows up. Everything is active, on, etc. I get the one to show, but not the other... what the heck?

Ok, just to test things and see if I'm crazy, I set up the same thing on the home page (this time using the "filters for homepage" block). Same thing as before... I go to add both of my filters but... the price filter is not available to choose? What?? Only the "size" option shows up?? Ok... well, just for testing, lets add that... so I do. And sure enough, the "size" filter is there on the home page. Except.... the drop down options it provides the user are strange... I have no idea where its pulling the options or how to adjust them. It seems like its trying to provide some (not even all of them) of the variations available on one single product. Is this where it tried to populate the list from?

So I'm all turned around here, anyone able to point me the right way? I feel like I should know how to get what I want done but it just doesn't want to do it.