In iNEXT Package of R, plotting Rarefaction /Extrapolation curve based on incidence data by default it is double of the reference sample. Although my plot not shows any definite conclusion on extrapolation upto double of reference sample. Therefore I want to increase the extrapolation. How much can I extrapolate : Double of total reference sample or triple or more of lowest sample (habitat) or double of highest reference sample (habitat) or any others? Give reference. Thanks in advance.