Cell Temp versus Ambient temperature in string voltage sizing

[IB31]

I am looking for clarification for the string voltage sizing calculations in PVsyst. The Maximum and Minimum temperature in the project setting window is ambient temeprature value or Module/cell temperature . If it is cell /Module temperature (as per help) then does user need to find the cell/ module temperature using ambient temperature using the IEC 68153 which is bit tricky because it is dependent on Irradiance and coefficients.

PVsyst does calculate the module temperature hourly but can user input the min and max cell temp values in the project setting window without much of calculations.