It is confusing. You answered correctly (no), that you were not covered by a HDHP as of 12/1/16.
On the Max Contribution page, you would select self-only for the months Jan - Oct, and none for Nov-Dec. and then select the Calculate Max Limit button.
This will calculate your maximum contribution limits for just your covered months. There is a penalty calculated if you were not covered by an HDHP and over contributed to the HSA for the non-covered months. A $20/month contribution should produce no contribution penalties.
See below example.
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