Your level, and why Carna asked your birthday
The date of birth on your profile picks your starting level. Here is what it does and does not do.
When you finished your profile, Carna asked for your date of birth. That answer is used to choose the level you start at.
Why age at all #
Because a ten-year-old and an adult at the same English level should not get the same lesson. The grammar may match; the subject matter, the examples and the tone should not. Age picks the shape of the material, not how hard it is.
It is a starting point, not a verdict #
What you actually do moves you. The date of birth gets you into roughly the right place on day one so that the first lesson is not absurd in either direction.
If it is wrong #
You cannot change your date of birth yourself — it is not in your settings on purpose. Ask your teacher or your school's administrator to correct it. See Change your name, picture, email or password for what you can change.
If the work feels too easy or too hard #
Tell your teacher. They can see your reports and move you. Do not sit quietly at the wrong level for a term — it is the single most common thing that wastes a year.