AF 60mm/2.8D problem

[LiTao(Aron Li)]

Hi,
  I've got a new AF Micro-nikkor 60mm f/2.8D. When I use it to take
close photo, I found the aperture value from the screen is not 2.8 while
the aperture scale is 2.8. I used the Nikon F70D body. It is 4.0 at 1:2
position while the scale value is 2.8. Is that somthing wrong with the
lens?

Li, Tao