How many stanzas and lines are in this poem? I can't figure out the difference! Please Help!?

Question

Sylvia Plath

Mirror

I am silver and exact. I have no preconceptions.

Whatever I see, I swallow immediately.

Just as it is, unmisted by love or dislike

I am not cruel, only truthful –

The eye of a little god, four-cornered.

Most of the time I meditate on the opposite wall.

It is pink, with speckles. I have looked at it so long

I think it is a part of my heart. But it flickers.

Faces and darkness separate us over and over.

Now I am a lake. A woman bends over me.

Searching my reaches for what she really is.

Then she turns to those liars, the candles or the moon.

I see her back, and reflect it faithfully

She rewards me with tears and an agitation of hands.

I am important to her. She comes and goes.

Each morning it is her face that replaces the darkness.

In me she has drowned a young girl, and in me an old woman

Rises toward her day after day, like a terrible fish.

Answer 1

I have had some editors count the 2 spaces (double space) between the stanzas and call it a 20 line poem. I'd like to see a hard and fast rule on it.

Answer 2

2 stanzas, both containing 9 lines.... so thats 18 lines total.