Limited releases are in play for 12 weeks and Wide releases are in play for 4 weeks.
Adjusts are an interim realignment of the stock value. It is expected that, on average, movies released in wide distribution will make approx 2.7*their OW box office earnings (for a two day weekend). Other lengths of release have different multipliers.
When a movie is over/under priced, OW adjusts are used to bring them in line with reality. YOUR job is to guess the openers...that is to say, figure out which ones are over priced and which ones are underpriced. You stake your hard earned H$ against your opinion by longing or shorting movie openers. After that, the price of the moviestock is reflective of what players believe the movie will delist at.
There are many tools available to help predict the weekend box office, in the form of websites. HSX provides a prediction every week as well. some are more accurate than others.
http://www.leesmovieinfo.net/movie-predictions.php
http://www.boxoffice.com/
http://www.filmgo.net/BillsBoxOfficePredictions/tabid/138/BlogID/6/Default.aspx
HSX uses ERC for their official results and they offer a prediction as well:
http://www.ercboxoffice.com/
I hope this helps serve as an introduction to the topic. Other players will be able to expand on this "foundational" information. Good luck!