It’s hard for me to judge from the images alone but it looks like you have a very large world which is also very sparsely populated. This isn’t really the problem the plugin was designed to solve, and in your case a sparse octree might be preferable. That’s the first I’ve seen of that font issue, I’ll look into it.
The values are clamped because once you get too far from the world origin, you are going to have problems with precision anyway and will have to use origin rebasing and/or world composition - or some other custom solution that keeps the player camera at the world origin and moves everything else around it. Space games can’t really work in the way a traditional game does, once it gets to a certain size you have to break it into chunks anyway.
If you like however you can easily unlock the clamps by going into ST_SparseGridData.h and set ClampMax and UIMax to something larger (full source code for the plugin is included, just move it into your project and change those lines).
The absolute maximum for the cell-count values will be 4096, but I really wouldn’t recommend that because that would result in over 16 million cells, and the heatmap tool would be extremely slow. The heatmap tool only works when you are playing in PIE, as there is no manager when in the level editor - it’s just there to help you visualize the density of objects when the game is running.