Well, yes. You want the required to be less than the actual, right?
Still, I think I might know what's going on. There was a lot of radiation damage on that one. (Another NPR did it. I try not to break things that I want to steal.) I had enough troops to prevent unrest from insufficient occupation forces, but not enough to overcome all the unrest from radiation. I'm thinking that maybe it won't move up the scale toward Imperial Population unless the political stability modifier is 100%? So I've added more occupation forces. Now we're at 570 required and 689 actual, enough to keep the political stability mod pegged at 100%. Here's hoping that does it.