Big difference in "free parameter" (np) in Sites Models for different models with CODEML (PAML)

Question

[mauricio.1313]

Hi PALM users!

I performed Sites-Models for my data and I did LRT to evaluate the best model. The abstract of my results is in this table (add figure). Some models have "free parameters" (np) equal to 5 or 16, however, other models have a value of 1454.

This is normal or an issue? What mean these big differences in np between models?

Please, any suggestion or comment is welcome! Thank!