Apologies for the delayed response - we must have missed this post. This behavior is by design - the control treats the center of the cells as points for the contour grid. We were not able to replicate the offset of the contour lines - the following picture shows the output of the current version of the control:
An alternative behavior will probably be to treat the corners of the cell as points in the contour grid, but then there is ambiguity for what is the value of points that belong to for adjacent cells. Let us know if you have any questions.
Nevron Support Team