Was the other pilot an instructor? Was it a proper instructional flight? If not then you weren't under instruction.
Since (a) the aircraft does not require multi crew and (b) you are not type rated, nor class rated, you cannot claim P2 time.
You can put it in your logbook as 'other' but the time does not get added to any totals, doesn't count towards any of your revalidation requirements and is only really there as a diary entry for when you handled the controls of a Caravan under the supervision of the PIC.