LM61460-Q1: Thermal Information, R value

Hi Experts,

Could you please help customer's questions?

1.

The Thermal Information of LM61460-Q1 is like below.

The condition is 4 layer PCB.

Does the R value go down If it is 10 layer? Specific data. would be very helpful with 

2.

What is the "Charaterization parameter" ?

Thank you.