Understanding Ranked Placements

I very frequently see people rage posting about how they won 8/10 provisional matches and still got placed in Bronze 5. Well, it kinda makes sense. Here is what I just experienced:

I just started ranked. I won 5 and lost 5. Got place in Silver 3.

Here is why I think this occured: I played many normal games before and my MMR was quite high. I had gold and platinum players in my FIRST provisional match. Most likely, a loss on that round still had me in high gold. Only after enough losses was I lowered to silver.

I think you don't "start at bronze 5" rather, you start at your MMR and your rank is adjusted based on your wins and losses.

Is this accurate?