3 units is still considered full time so it's ok, but you should really have 4...so perhaps you should be enrolled in something else...or you have a free elective that you haven't yet chosen or enrolled in? I would contact the unit co-ordinator to make sure, as if you are meant to be enrolled in 4 units, you will have to make up the other at a later date, which will mean 5 in one semester or summer school.
My status is ok...but I've been attending classes for over 2 weeks now...if it doesn't clear up in a few days when the teaching session has well and truly commenced, check to make sure your enrolment is 100% complete.