I booked a train ticket on IRCTC from Ghaziabad to Lucknow for date 19/09/15
2 days ago the Current status in PNR was WL 28.
Now suddenly it is showing Current status RAC 80, (Booking status W/L 68, GNWL).
All the passengers in a ticket are assigned a ticket status which can be waiting (WL), RAC (a half berth), or confirmed (full berth). These are explained below in detail: Waiting List (WL): If the passenger status is marked as WL followed by a number then the passenger has a waitlisted status.
with a RAC ticket, you will be able to board the train legally and will have to share a berth with someone else. It's likely that you will get a confirmed seat by the time chart is prepared. Do check out the trainman link given by @v1rus