Bug in Polar RS200sd

Let met start with stating that I am very satisfied with my Polar however....

On this image from the manual you can see that the polar RS200sd registers both the average and the maximum speed per lap. Small digits in red outline is average, large the maximum speed.


On my polar I find from time to time that my average speed is higher than the maximum speed. Could be that I didn't pay enough attention in highschool but I don't think so. So a bug in the RS200sd?
See the image: 9.1km/h average versus 8.5 maximum...