understanding duplicates statements

hello gurus !!!!

       I would like understand duplicate statement. in my OEM screen I have got :

I see in my screen OEM the duplicate statement : this time 41 and sometimes 250.

Then I would like understand if it is a problem or not : but I suppose, yes, because it is in memory.

1 - I do not understand why it is the same plan hash value ?

2 - if it is the same plan hash value duplicated, why Oracle OEM appear duplicate statement ? because for me it is the same query.

3 - how may I see if it is a problem or not ?

4 - I join you several screenshoot for it and better explain to you .