Everyone gets tempted to over-specify job titles on LinkedIn. Say you sell payroll software and target only "Finance Manager": the people who actually sign off are often a CFO or an ops director, and they never show up in that filter. Narrow titles also shrink the audience so much that the ad sets struggle to learn, and cost per lead climbs for reasons that are hard to spot in the dashboard.
I'd go broader on title and tighter on company size and industry, then let the lead form questions do the filtering. Seniority filters can help, but on a small budget I'd be careful about stacking them. The test that matters is whether the broader version produces leads sales actually closes, not just cheaper form fills. Has anyone seen the opposite on a niche product?