The foreclosure list price is a guide --- but the actual price it will sell for can be over or under the list price. It all depends on the location, price range, how much it's listed for (is it close to what the lender paid for?). What are the comps.
In the under $300K range, several times, my clients and I have found ourselves in competing situations where the actual and final sale price is above the list price. Just today, the bank countered three offers and asked for our best and highest offer. This is an anomaly. Usually, the bank simply picks the best/highest offer and doesn't counter the others. So we are actually surprised to get the counter.
There is no standard of how much less (or more) your offer should be. Have your realtor do the research --- what the bank paid for the property, what the comps are, are there other REOs and short sales in the vicinity and how do they compare to the property, etc.
Then determine what you consider a fair price, and turn in your best and highest offer. You may not get a second chance, so make it a strong offer.