I need to add an addendum/clarification to this answer. Originally, the guidance about numbers with a + or – in front of them did not say they had to be done in Nemeth. A change was made to the guidance that was recently updated and approved by BANA making it clear that any number that is modified mathematically (meaning it has a +, – or even a $ or %) should be done in Nemeth when using the Guidance for Nemeth in a UEB context. If these types of numbers come up in a literary text, they can be done using UEB symbols.
Cindi