Quote from Hideout:

As far as low dose you have to look at two things - the estrogen and the progestin. The estrogen, anything less than 50 mcgs is a low dose. Ovcon is 35 mcgs hence the name Ovcon 35.
The progestin - .4 this is the lowest progestin of any other pill out today.

Different progestins have different "strengths" so some do not need as much to have the same effect as another progestin might.

That is to say that the progestin in Ovcon 35 is not "lower" then other pills in terms of its action in the body -- it is the just that the progestin in Ovcon 35 requires less of it to achieve the same action as the progestin in say, Demulen.