Creep Constants

I am trying to determine the constants described in the help file to model creep life with simulation. Does anyone have any experience doing this? So far, I haven't been able to find a valid solution using a system of four equations. I found the link showing an example problem where C2 is assumed to be 1 (http://www.motovated.co.nz/newsletter/aug13/FAQID__x394.pdf); the only problem with this is they say it is usually safe to assume C2 = 1, but don't say when it is not. Below is an image of the creep life data we're using to determine the constants. We will be using Heat No. WWS.

Any help would be greatly appreciated.

SolidworksSimulation