The furnace class is per figure a at the bottom of page 11
You just go by what ever is the tightest tollerance by all the specs you work to. IE if one spec is +/- 25 and you also work to another that is +/- 15 the class would be 3 since the +/- 15 is the tighter one and would cover the other.
The type is is determined by looking at what you have for your TC set ups on the equipment you have.
For a good pyrometry class I would recomend the PRI one. It even makes sense to a beginer and realy helps you understand