Thermal Mastic is a must-use product when a cooling unit is installed to give the correct transfer of heat from the interior of the refrigerator to the coils leaving the cold. I know it does not sound correct, but a cooling system does no produce cold, it removes heat. Once the heat is removed an what's left is cold cold. The more heat removed the colder it will be.
One tube is more than enough for a cooling unit to change our job.