Thanks for your interest.
The process is as follows:
Two base liquids, liquid1 is on relay 3 and liquid2 on relay 4
Liquid2 is always neat, whereas liquid1 may be neat, but can have one of three additives,
Hence relays 0, 1 and 2
Relay5 is for purging the line.
Ultimately The code needs to ensure that each button calls the correct sequence and prevents any other simultaneous button call.