Surely it won't matter for the QSLs.
As far as the contest itself goes, it is unlikely to cause any trouble, especially if you do not send in a log. Even if you do submit (and you supply it in Cabrillo format as you are supposed to), as long as the submitted QSO data reflects "what you sent", the log checking should simply compare the "incorrect" (but actually sent) number (and not the actual chronological number) with what is logged by the other station(s).
Personally, I wouldn't worry about it, but you could always ask the contest director... firstname.lastname@example.org
73 Mike N2MG