TPS54560: the difference between ψJT=5.9℃/W and θJCtop=45.8℃/W

Part Number:TPS54560

Hi team

Would you mind if we ask TPS54560?
We are sorry for asking the similar question many times.

The datasheet shows ψJT=5.9℃/W and θJCtop=45.8℃/W.
Why does TPS54560 have the difference between ψJT=5.9℃/W and θJCtop=45.8℃/W?
Because, Ψjb=23.4℃/W and θjb=23.4℃/W are the same value.

We appreciate your help.

Kind regards,

Hirotaka Matsumoto