BM-T02 is to extend four-channel, you must have the BM-T01 to run this.
Option One: a BM-T01, 3-channel functionality with a computer-controlled dosing
Option Two: 1 BM-T01 + 1 BM-T02 = 7-channel computer-controlled dosing function
Program 3: 1 BM-T01 + 2 BM-T02 = 11-channel computer-controlled dosing function