Dilation & Thinning Question

If I was 1cm dilated at 33wks (closed at 28wks...(having bad contractions both times so was checked cause of preterm history)

But was 3cm dilated and 0% effaced at 36+2....

How can I be dilated....but not thinned out at all? Don't you need to be somewhat thinned out in order to dilate?

I have multiple children already.

PLEASE EXPLAIN BY THERE DIFFERENCE..THIS IS WHY I'M ASKING LOL. I obviously know there 2 different things.