Why is every text message my wife is receiving is accompanied by the number 2300

Every text message my wife is receiving there is another text that is the same time as the text message. It's usually the number 2300. For instance my wife receives and incoming text at 9:52am from 999-777-5555 and there will also be another incoming text at 9:52am also and it's usually the #2300. ¿Por qué?