Bodies actually rendered/selectable right now — see visibility.ts's computeVisibleBodyIds and labelDeclutter.ts's screen-space thinning, both applied before this count is taken.
totalBodies - visibleBodies — how much the LOD/crowding gate and screen-space thinning are currently hiding, the "cropping" a dev overlay exists to make visible.
Bodies with a currently-shown text label (a stricter subset of visibleBodies — see labelDeclutter.ts's thinByScreenProximity).
Real tracked positions across every belt/cloud region (e.g. named asteroids within the main belt) — rendered as instanced points, not individual bodies, so they're counted separately from totalBodies.
Every body defined in the system's own data, regardless of whether it's currently rendered — the "total" a viewer would otherwise have no way to know from an already-thinned scene.