Consider this EXPLAIN ANALYZE fragment. What does the gap between the planner's estimate and the actual rows tell a senior reviewer?

Seq Scan on orders (cost=0.00..18.50 rows=5 width=40) (actual time=0.011..2.317 rows=5000 loops=1) Filter: ((status = 'open') AND (region = 'EU')) Rows Removed by Filter: 120