You can adjust the axis range in a 1D blend space to be from any number (min) to any number (max), but the editor will crash if you set the minimum range value to anything but 0, save the blend space, then later try to re-open it. The editor crashes on re-open.
Thank you for bringing this to our attention. I was able to reproduce the issue here and have generated the following bug report: [UE-5546] When this is issue is resolved in the future, an update will added to this post.