To expect a value of 200 means to have the average of 200 from this point in time onwards, assuming stock price is random walk. Not that the value tomorrow will

To expect a value of 200 means to have the average of 200 from this point in time onwards, assuming stock price is random walk. Not that the value tomorrow will be exactly 200. It could be 200, 201, 199, 202, 198 etc. the average expected is 200. If you possess no external knowledge such as insider information, then random walk is a sensible and obvious choice for stock price.