OR inside, AND across
Pick two seniorities inside the Job Seniority facet and LinkedIn shows anyone who is either, so the audience grows. Add a second facet, say Industry on top of Seniority, and a member now has to match both, so the audience shrinks. Every separate facet you stack multiplies the narrowing, which is how a healthy-looking audience collapses to a fraction of itself.
The double-cut trap
Some facets encode the same signal, so stacking them cuts the same people twice for no extra precision. Job seniority and years of experience are the classic pair: a title already implies seniority. And even the narrowed number overstates delivery, because LinkedIn says the accounts you actually reach are fewer than the target audience size. We work through both in the LinkedIn audience number is not your audience.