As far as I can judge, + means "these games involve the same Link" and - (a hyphen, not a minus sign - that's assuming it isn't an underscore) means "these games involve two different Links". Derived from this is the fact that games joined with a + take place in close succession, whereas games joined with a - tend to be considerably farther apart in time.
As far as "arranging all the notes" goes, it wouldn't surprise me to learn that this actually did get written out on a blackboard and we're looking at a photograph. If for no other reason than that I don't think I've seen an image-program brush tool which is capable of looking that much (and, importantly, that inconsistently) like chalk marks.
As far as "arranging all the notes" goes, it wouldn't surprise me to learn that this actually did get written out on a blackboard and we're looking at a photograph. If for no other reason than that I don't think I've seen an image-program brush tool which is capable of looking that much (and, importantly, that inconsistently) like chalk marks.