The pressure at the center of the surface low has decreased from 960 mb to 950 mb.  Because the surface pressure is lower the surface winds have strengthened. They are now each adding 12.5 mb of air instead of 10 mb.  Now a total of 100 mb of air is being added (50 mb at upper levels and 4 x 12.5 = 50 mb at the surface).  100 mb of air is being removed at upper levels.  Addition and removal of air are in balance.  The surface low pressure won't change any more.