Every article earns acorns. Very very short (like less than a paragraph) articles will get an acorn. Long full length articles get 50 acorns. And then there are other amounts for the in between lengths. The system automatically decides each one based on the word count, and Trish has the power to over-ride that and award more acorns than the system would automatically assign.
My CB4L article yesterday received no acorns because I posted it in the middle of the day. Usually when we do something like that we manually give the acorns but since it was "just me" I decided not to.