Connector - temperature rise

Hi Everyone.

I try to define the "insert temperature rise" for the connectors.

Simply Delta T = a * Icontact1.85

But, i dont konw how to calculate 'a'.

The sequence I calculated was 

First, define AWG to connectors.

second, fine 'a' to common gauge values table for AWG

However, the AWG values in the common gauge values table are incremented by 2, so I can't find the value of 'a' that I want.

how can i do calculate to "insert temperature rise"?

Regard

Inhae