Confused on Grouping Games Rule Diagramming Drill

[srr021]

Hello! I have the 2017 edition of the LG bible and I had a question about the diagraming of a rule from page 283. The rule states "Either F or G, but not both, must be selected". It is diagrammed using the double not arrow. I thought this could not be used to diagram the rule because that symbol indicates that the both F & G can be out, which cannot be the case since one of them must be selected. Am I misunderstanding the symbol? Or was there a mistake? Thanks in advance!

[Dave Killoran]

That is capturing the "not both" part. The other part is shown directly on the diagram with the F/G on the Group of 5 selections. not everyone shows the "Non-selection" group, hence the redundancy there

Thanks!