If you are designing a new stair you may want to check if it complies with the minimum height clearance rules that apply in your country.
This is very easy and helpful with the Cadimage Stair tool, just go to the Settings > Head Clearance Plan
For ARCHICAD 20
Settings>Symbol>Head Clearance and edit the minimum height.
For ARCHICAD 19
You can control the display of this clearance according to the Model View Options or by the Settings
This is how it look in a section