Hi there

Under a drawing environment, i made a smart dimension from a edge to center mark of a PEM nut, turn out 9.42mm. but when i applied a vertical ordinate dimension between same edge and center mark, turn out 8.79.

and i measure the distance under 3d environment, the value  was also 8.79.

shown as below Pics.

Did anybody meet this thing before?  how can i fix it?

i attached my files.