What is the meaning that "I do bring a certain credibility to the role."?

 i read the underlined in that script. but I can't make sense it.
 I thought it means that Lennart tell Joey that he do his best to the role.
How about my thought?
 Would you show me about what the underlined means?

--------The script goes:
Receptionist: This is Joey Tribbiani. Joey, these are the producers and, as you probably already know, this is Lennart Haze.
Joey: It is so amazing to meet you. I'm such a big fan of your work.
Lennart: Well, I've… I've been blessed with a… a lot of great roles.
Joey: Tell me about it! "Unlimited nights and weekends!"

Lennart: Are you making fun of me? Because I am not a sell-out. I didn't do that for the money, I believe in those phones. I almost lost a cousin because of bad wireless service.
Joey: No, I-I-I wasn't making fun of you, honestly, I-I think you were great in those commercials.
Lennart: Really?
Joey: Yeah.
Lennart: Well, I do bring a certain credibility to the role.
Joey: Are you kiddin'? When they shoot you out of that cannon…

Lennart: Peeeeeooooooooch "Hang up that phone!" One take!
Joey: Wow!