AIBU to wish that the abbreviations (which I don't personally like anyway, but I understand why people want to use them) were used consistently?
Sometimes it is not clear whether DD3 is the poster's 3rd daughter, or an unspecified number daughter who is three years old, as people don't always put ages in brackets. And it is often relevant to the thread.
Obviously with the higher numbers it becomes increasingly unlikely (though not impossible, especially if they say DC rather than breaking it down by sex) that they are talking about birth order rather than age.
And sometimes it is obvious from what the child is doing (e.g. a DD2 who is refusing to revise for their exams must be a teenage second daughter, not a 2 year old).
But still.