Soft refers to effacement, which is typically measured in percentages. It probably means that you're just not measurably effaced yet, but that you will likely be soon.
Closed but soft (or any measure of dilation and effacement) doesn't really give any indication of when labor will begin though. You likely have weeks to go regardless of what your cervix is doing just because most women won't give birth until around 40 weeks or so anyway.