Question about Galloway Magic Mile & intervals

Hello,

I've been training for my first 1/2 marathon which will take place on 3/2. Today I did the magic mile for the first mile of my run.

Magic Mile: 12:37
Half Marathon Training Pace: 18:24
Half Marathon Pace: 15:08

Here is where I'm confused. I'm currently training at a 2:1 run:walk interval. I started my training with that flipped, 1:2. Slowly reduced the walk until I was 1:1. Now have been increasing the run to my current 2:1 interval. I know my run portions are getting slower because my overall pace in my training runs is basically the same. (Plus I can see it on runkeeper).

This is what Galloway says about run:walk.

12 min/mi run 2 min / walk 1 min <

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this is what I'm running interval wise, but that is not my training or race pace
13 min/mi run 1 min / walk 1 min
14 min/mi run 30 sec / walk 30 sec
15 min/mi run 30 sec / walk 45 sec <

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this is my race pace
16 min/mi run 30 sec / walk 60 sec

The 18 min/mile pace doesn't even have an interval listed!

Am I supposed to be running the 2:1 because that was my magic mile pace ish? The 30sec:45sec because that is my race pace? Or something else altogether to train at the 18 min/mile pace?

Thanks for any help/feedback!