Water to Air heatpump curves - cooling mode

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In energyplus or OpenStudio, when editing Cooling performance curves of Waterto Air heatpump, there are only 5 coefficients for both "Total cooling" and "Cooling Power". Only Sensible Cooling has 6 coefficients. I know that all the curves are Bi-quadratic, then normally they have 6 coefficients. So the question is: How do I treat data when generating my own curve. Generate 6 coefficients then use 5, abandon constant value. Or tell excel to force constant to zero ?

Thank you.