How are checksums saved?

[EmmanuelMess]

How does this database save the checksum algorithms for Air Conditioner messages?

[probonopd]

I am not sure I understand what you mean by "checksum algorithms".

The protocol/device/subdevice/function notation is a way to specify the exact IR code that should be sent to control a particular electronic device. By using this notation, software like HARCToolbox by @bengtmartensson can generate the correct IR code for a given device and function (presumably including any checksums, should they be needed), allowing you to control it using a compatible IR transmitter.