If you intend to support Galaxy Tab 7, the original version with Gingerbread, I would say that there is no way to support only a tablet for Gingerbread. Because Gingerbread does not have clear tablets and phones.
From Honeycomb alone, the smallest dp width can be used to indicate the difference in width.
So, I think this answer may help you:
Android Application Development with Android Support
Basically, you need to add a minimum SDK tag to restrict only Honeycomb (only tablets, phones with a cell phone), and you can download your application
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