My DVC run to much and finish the show too early

[Clues Hunt]

I bought a DVC fun with the dry connection because I need to use it in stand alone mode.
I discover that it play the show in only 50 minutes and 4 seconds but it need 60 minutes. Is it normal? Is my DVC fun broken?
I think that isn't normal that it take only 50'4" for to play a show of 60'!