INDEX BUG???

hello All

I tried the following commands:
ponto=# explain select * from horarios where funcionario>10000;
NOTICE:  QUERY PLAN:

Seq Scan on horarios  (cost=0.00..176.21 rows=2432 width=132)

EXPLAIN
ponto=# explain select * from horarios where funcionario=10000;
NOTICE:  QUERY PLAN:

Index Scan using horarios_func_data on horarios  (cost=0.00..55.37 rows=73 
width=132)

EXPLAIN

So my question is why in the first case the postgre did'nt use the index 
and made a seq scan ??

thanks and sorry about my english...