Hello Steve,
When you import to Excel you'll get two sheets. First sheet consists of list of tags and second sheet consists of Settings information. It will be done to get possibility to Export and Import complex tags trees with groups and subgroups. The second sheet contains "The number of tags are used" parameter. You have to change this parameter also when adding new tags. Also you have to watch that name of new tags not to be the same of existing tag's names.
Best regards,
Ruslan