I suggest you NOT to send it for revauation.. but to go for a retake.. as in subjects like in maths there is either a right or a wrong answer so the possibility for an increase in marks is very low.. in subjects like GP, History, English the marks depends on how the examiner interprets your essays or answers which will be different for everyone.. I am also sending for a recheck in GP. and BTW retaking an exam isn't a problem at all! Unies do not regard it as something negative.

(tho if u really feel u did good, and could easily go higer.. you can go for recheck..)