Here is what you hit or very very similar. I just did it with these written directions on my desk a few days ago.

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-you may have to hit do it
-in the command line its waiting for you to type in x,y go ahead and type in 80,160 or whatever numbers you need.
Do It and your done.

I redid one from 10,000 x 8000 so you should not have issues with a smaller scale.

Not too bad, g'luck
JJ