Accepted to UCSD as "Undeclared" major?

Transfer Students UC Transfers
1

I applied to UCSD as bioengineering but was accepted as undeclared. What exactly does this mean?

2

I could be wrong, but from what I understand if you get admitted as undeclared even though you declared a major it’s because they already filled that major but they still want to accept you as a student. What it means more than that I’m unsure.