It is a relationship status commonly used in Hong Kong, especially for the university students.
The letter A = Available. You are single and okay for starting a relationship
The number following after the letter = How many times you have been in a relationship.
And if you currently are in a relationship, then the status would be started with the letter "O" = "Occupied".
For example, if you are currently in a relationship, and it is the first relationship you have. The status would be "O1".
If you are single right now, you had been in 3 relationships before. Then it would be "A3".
There is also other status called OBA , "Occupied but Available". A term for people who is okay for being in more than one relationship at the same time.
βA0β is pronounced as βA-lingβ in Cantonese, which vaguely resembles the English word βAloneβ. Colloquially used as an expression of being single.
The number after the letter βAβ could also be used to refer to the amount of times one has been in a relationship. For example, A1 means that a person has been in a relationship once, and A2 means that a person has been in a relationship twice, so on and so forth