What is the meaning of "Super-Critical Discharge Coef" and "Sub-Critical Discharge Coef"

What is the meaning of “Super-Critical Discharge Coef” and “Sub-Critical Discharge Coef”

Hi cuizhenyong2020
“Super-Critical Discharge Coef” and “Sub-Critical Discharge Coef” regarding the two formulas in the figure I attached below,


Sincerely,
BMHoa