It means you are the 51st person to book in wait list.This is called booking status.
But some people have already cancelled their ticket and hence you current waitlist ticket number is 27
Booking status will remain as is. Your current W/L number will move further up.

27

thanks Mr. birari and one more thing i want to ask what is CK, GPWL, PQWL, RLGN??

CK is Tatkal quota
GNWL is General Waitlist
PQWL is Pooled Quota Waitlist
RLGN is Remote location Waitlist

actual status is WL 51 and current is WL 27