Configuring Modbus to read a register of type 'ENUM8'

Hi All,

Does anybody now the difference and location of the folowing registers for a heatpump (Remeha Eria Tower ACE S)?

AM016 → 400 INT16 Supply temperature unit
AM018 → 401 INT16 Return temperature unit (0 no reading, does not work)
HM001 → 403 INT16 Supply temperature heatpump
HM002 → 404 INT16 Return temperature heatpump