Thread: Why do the enum values this way??

Code:

enum tx_op {
        P_TX = 1,
        PU_TX = 1 + 1,
        RT_TX = 1 + 2,
        GET_TX = 1 + 3,
        PUT_TX = 1 + 4,
};

What's the purpose of the 1+1, 1+2, etc.. why not just do 2,3,4......??