if you are in the 33rd percentile for both height and weight, you are taller and weigh more than 33% of all adult females (assuming you are an adult yourself. if you are not, the classification would likely be made within an age group).
I would not go by that. You'd be far better served by going by your bodyfat percentage. It's a much better indicator of progress than any measure of bodyweight. If you can't go by bodyfat percentage then you'd be go by measurements instead of weight.