It is possible that they had a valuation done on the property and found it to be lower than your offer.  If this is the case and they are looking to not have problems selling the property, they are reducing the purchase price to the point they feel there will be no problems.

It could also be that someone made a mistake.

Either way, don't look a gift horse in the mouth.  The bank would disclose any problems that they are aware of with the property.

How did you come up with the offer?  Did you do a CMA? 

Be careful.  It is also possible that if the condo needs repair and the lender does not want to cure, they have discounted the value accordingly.  If you are prepared to repair upfront, this maybe a good deal for you.  Keep all your receipts and you may have a writeoff on your tax returns.  Check with your tax consultant or IRS for more details. 

It might be best to check the property because there might be something that you do not know. If you already have, visit it again and look for details you might have missed during the previous visit. Anything you find concerning repairs and the like should tell you why a counteroffer was lower.