This field lacks a question-mark to expand a description from.

For the benefit of others, you need the value under the "Group Name" volume of the Security Groups screen within the AWS web console. It seems that this field is in fact read-only, at least within this interface.

Ignore the "Name" column (which can be changed by others so should never be relied on) and the "Id" column (which I would suggest was a more natural expected value for this field, however).