Mailing Recipients field only displays 10

Discovered this under Wordpress 4.8.3 running CiviCRM 4.7.27, confirmed on a second site as well as the demo (http://wpmaster.demo.civicrm.org) which claims to be running 4.7.29.   When setting up a mailing, the recipients field will only display the first 10 groups included or excluded alphabetically.  If you add an 11th group if it is alphabetically after the ones that are there then it doesn't show, if it falls alphabetically before or within the ones that are displayed then the last one gets pushed off the list.  The estimated number of recipients does update, implying that it acknoledges the group was added.  However, and this is the biggest issue from my testing, only the 10 displayed will be removed from the list of available groups to add, making it difficult to determine which groups have been included or excluded.

I will confess that I haven't tried sending the email to see if it actually goes to all of the groups that are added.