It does NOT say that!
Do you not know how stats and the questions work?
The question in the census was:
What religion are you?
They did not have 'Atheist' included.
The question that would have given the TRUE result would be:
Do you believe in God, and if so what religion are you?
...and include in the possible answers 'None'
They did not do that, so the figures are incorrect for the true reflection of the publics beliefs, as the question did not entertain that notion, it surmise all those forced to be Christians when kids are Christians now.
Very simple to understand.