A PQ 11 planet will continue to grow (provided morale is good) to a population of 34.6b. So it's not only fine, you have a lot of room to go.
The tiles that required soil enrichment will not be the same tiles that require habitat improvement. Also, there is a display bug that does not show the planet's correct PQ when you load a save (vaguely remember the details of that thread). but if you count the actual tiles you can build on, you should count the correct number. I don't recall ever seeing a PQ planet that nice in any of my limited number of games yet, so not sure if there is a PQ cap that comes into play with that one.
