"Not supported by data" and " Collapsed rate class " in the log file

[aaannaw]

Dear author,
I noticed the log file showed the information:

• The following rate distribution was inferred for test branches

|          Selection mode           |     dN/dS     |Proportion, %|               Notes               |
|-----------------------------------|---------------|-------------|-----------------------------------|
|        Negative selection         |     0.000     |   88.606    |                                   |
|        Negative selection         |     0.999     |    0.000    |       Not supported by data       |
|      Diversifying selection       |     1.000     |   11.394    |       Collapsed rate class        |

* The following rate distribution was inferred for **reference** branches

|          Selection mode           |     dN/dS     |Proportion, %|               Notes               |
|-----------------------------------|---------------|-------------|-----------------------------------|
|        Negative selection         |     0.000     |   88.606    |                                   |
|        Negative selection         |     0.001     |    0.000    |       Not supported by data       |
|      Diversifying selection       |     1.911     |   11.394    |                                   |

What does mean the information for "Not supported by data" and "Collapsed rate class" ? Should I trust the relaxation or intensification result (K value) and the dN/dS value in the json output file? Could you give me any suggestions?

Best wishes,
Na Wan