On your burner knob, medium-high (medium high) is half way between Medium and High. I don't think the hyphen makes a difference.
Would it make a difference if you went from Medium to Medium-High, or should you turn the knob from High back to Med-High? There might be some play in the knob.
As an editor, I would interpret the hyphen to mean medium-high. If it is an en dash, I would interpret it to be a range from medium to high (so it would include any and all settings in between). En dashes are slightly longer than hyphens. Whether an en dash of hyphen, there should not be any spaces, but oftentimes you will see en dashes when representing ranges written with a space after the first word/number and after the en dash.
If it is in a printed book, the editor would be aware of this. If handwritten, anything goes. In-house style guides often have the editor removing the "to" and using the en dash in its place to represent range.While I'm not questioning your statements above, I doubt the majority of recipe writers are aware of this. I see recipes written often in a haphazard way with no consistency. Horizontal line segments aren't always the best way to convey specific information as their meaning can be ambiguous.
so what is it a range or medium high?
so what is it a range or medium high?