Hi ABRXC,
Thanks for posting in our community and I'm glad to support.
We went through your post carefully and it seems like the concern is about editing the X-Axis in an Excel line chat. See: Change the scale of the horizontal (category) axis in a chart (microsoft.com)
We tried to deploy a similar environment to test the issue about "a data point of 17 appears to be positioned above the value of 10 on the x-axis". However, it seems like we failed to perform a similar test . Hence, we'd like to have some screenshots from your side so we can better understand the scenario and make sure we can provide the appropriate suggestions.
Meanwhile, may I further confirm the issue scenario about the display on your side after you click 'Select Data' for the X-Axis? Some few screenshots would be easy to understand.

Your understanding is highly appreciated and hope you a good day!! We will be here for you anytime to offer further support.
Best Regards,
Mia