there is always some error in the GPS.. you cannot add an offset as in some other location, the error may be in a different direction. You could check the specs on your GPS to see if there are more accurate models available
The position error is more likely caused by an inaccurate chart then the GPS. It looks like a CM93 cell, so read CM93 Offsets | Official OpenCPN Homepage
Of course make sure that your GPS is giving you a correct reading and the pier you are tied to really has the shape it shows on the chart before starting to freak out about every single chart cell you come across.