Thank you for your post.
At this time, FileMaker Pro will only chart data points. It will not weight the data to show a relative spacing between data points.
I suggest you enter this into our Feature Requests web form at:
Our Development and Product Management teams review these suggestions and discuss them for possible inclusion in a future release.
Although I could copy your post and paste it into the web form, there are some additional questions asked that only you can answer.