How to stop Google Keep from seeing numeric data as phone numbers?
Looks to be bad recognition by Google's code. :-/ Happens on mine as well and no setting can change it. 

Google is surprisingly receptive to feedback on its apps (a bug fix I reported made it into Google Music's update!), so two ways to get this fixed:

Go to Keep's page and click "Email Developer" and write this up. Or, within Keep, Menu -> Send Feedback.