As it gives a unique identification to each measurement.
Measurment-Object Report-Config Measurment-Id
1 (Carrier freq 1) 1(A3) 1
1 (Carrier Freq 1) 2(A2) 2
2 (Carrier Freq 2) 1(A3) 3
See each time measurment ID should be different for each unique measurement u do.