taxonomyextra table after migration from Drupal 6

Today there was finally time to delve into this issue.  First I downloaded the field_data_taxonomyextra table into a spreadsheet.  There is a column called Bundle, which in my case included, acidfree, gedcom, obit, and register.  Each bundle required a different "fix".  There is a column called entity_id which is the node number.  So I checked each node number.

The acidfree bundle nodes and gedcom bundle nodes could not be edited; clicking the Edit tab produced an error message.  Over time, I had apparently noticed these pages missing from their expected locations, and recreated them with a different node #, so these were no longer needed. They could not be deleted from the Edit tab.  My site has the Node Convert module installed, so there is a Convert tab near the Edit tab.  When I clicked Convert, I could see these bundle types did not have a Content Type assigned.  I converted them to a Book Page, and was then able to Edit the page, and Delete it. This action removed the row from the taxonomyextra table.

The obit bundle nodes and register bundle nodes seemed to be OK, but there was an extra field on the Edit screen that I didn't place there, "taxonomy upgrade extras".  This field had a word in it.  I cleared the field, saved the page, and this action removed the row from the taxonomyextra table.

The field_data_taxonomyextra table is now empty and I suspect it's Ok to be dropped/deleted.