Thank you for the question. It, unsurprisingly, has made me scratch my head. And, I have to amend my original answer.
Considering the updated example (4) in section 11.b of the Nemeth Code, numeric indicators should not be used in work arranged in columns for addition (even when the work includes equal signs). The updated example is below and is from page 5 of the 2007 Update to the Nemeth Code.