How to i write protobuf 0:0 message?

I don't understand how to write 0: 0 in proto message.

0: 0
0: 0
166: 9fc1171b9ae3179d4e
2: test
3: 1

I tried like this:

message test {
    int32 unknown = 0;
    int32 unknown2 = 0;
    ...
}