Wrong rows count in EXPLAIN

When I create a new table, and then I evaluate the execution of the SELECT query, I see a strange rows count in EXPLAIN
CREATE TABLE test1(f INTEGER PRIMARY KEY NOT NULL);
ANALYZE test1;
EXPLAIN SELECT * FROM test1;
QUERY PLAN
---------------------------------------------------------
Seq Scan on test1 (cost=0.00..35.50 rows=2550 width=4)
(1 row)

Table is empty but rows=2550. Seem like it was calculated from some default values.
Is this normal behavior or a bug? Can it lead to a poor choice of the plan of a query in general?