Using DBMS_sqltune Package To Tune Some Resource Intensive Queries

I am using dbms_sqltune package to tune some resource intensive queries. In this I am looking to know how Sql profile works

I created task for one sql using dbms_sqltune, then in Report it was recommended to accept its sql profile (which will potentially benefits 65%)
then accepted that sql profile with

exec dbms_sqltune.accept_sql_profile(task_name => 'pc1_61d2dhmdwzc8d', replace => TRUE);

and re-executed same query but NO difference in time. Then, what that mentioned potentially benefit 65% is about.

1) Originally query is taking 10 sec to execute, with this 65% i thought that it will execute within 3-4 sec. Is it right?
2)Also, the query for which i have created tuning task has some hardcoded input values, what if i change input values next time, will that profile works with new input values?

FINDINGS SECTION (1 finding)
-------------------------------------------------------------------------------
1- SQL Profile Finding (see explain plans section below)
--------------------------------------------------------
A potentially better execution plan was found for this statement.

Recommendation (estimated benefit: 65.17%)
------------------------------------------
- Consider accepting the recommended SQL profile.
execute dbms_sqltune.accept_sql_profile(task_name => 'pc1_61d2dhmdwzc8d',
replace => TRUE);