What does mobile phone number receive SMS priority test 2 mean?

In the short message center, it indicates the priority when sending short messages to the other party's mobile phone. When there are multiple short messages at the same time, the short messages with high priority are forwarded first. Short message is text or digital information sent or received directly by users through mobile phones or other telecommunication terminals. The number of characters that users can send and receive SMS at a time is 160 English or numeric characters or 70 Chinese characters.