New Speedy running fast - advice needed please

I tried to find out what the problem was but was told by Ruddells that they had just received information back to say that Omega had performed a full service and listed a number of parts that were replaced (which I'm assuming is standard when serviced). They have even put the red dot back on. Since receiving it back I've kept a record and performance varies day to day but is very good -

Test conditions - worn every day (I sit at a computer all day so not much activity), wound at 6.00pm, rested overnight, face up between around 10:00pm to 6:30am

First full day back total seconds gained +28 (was concerned!), then on the proceeding days (24hr periods)
+9, +10, +9, +8, +4, +2, +5 (the overnight part of these figures is usually 2 seconds)