iat vs start up iat

hi,

do you know the difference betweet "start up iat" and "iat"?

on a cad srx 2005, the temp gauge show normal when the engine is too hot, and vcm scan show too hot the real temperature so ECT is ok, gm tech2 show IAT at the real temps like 20 - 30?, but start up IAT allways -47?c.
the cluster gauge is tested ok... shematic show only one IAT and one ECT and they are fine, I found start up ECT too but it's same than ECT.

I don't understand what is this start up IAT and why cluster show normal temp when too hot.

thanks for your help.