frig temp adjustment.

I have a frig in my TT, don't ask if it's domectic or Norco or what, I don't remember but it has the temp adjustment on the panel out side above the door. it also has the sliding plastic with the wire on the frig fin right side. do I put the plastic fin half way up the fin or what. I noticed in our hot weather we are having the temp is in the low 40's and the plastic sleeve is down low on the fin. any body know which way to go. I have the out side control light on 3 or 4 not sure at the moment. I know I can raise the temp with the control
panel but would like to put the plastic sleeve in the proper space on the fin.