This has confused me. "This content may only have 20 tags in total". I get, at least I think. So, no more than 20 total. Ok, so, I can then "only apply 10 to this content"?
Multiple people can apply tags to a single piece of content. There are both global and per user limits. (It's possible you could only apply 2 tags in total yourself because 18 tags already existed, including ones you don't have permission to edit.)
After looking, I thought it was stating 20 tags could be posted in that area (as a rule or something), then the 10 meant only 10 could be applied (even though you have ability to put 20 in that box).
Multiple people can apply tags to a single piece of content. There are both global and per user limits. (It's possible you could only apply 2 tags in total yourself because 18 tags already existed, including ones you don't have permission to edit.)