With all respect, I did read your question, and I read your subject line. I answered the questions posed in the subject line. I read questions, I answer the ones I know the answers to.
I do not know the answer behind why there is no further detail in the Estimator. Perhaps it would be a good idea to clarify it as a "4 tire rotation" or something. I suppose you could submit feedback on the web site.
Most all flat rate manuals show .3hr flat rate time for a tire rotation, that would be 4 tires. Based on the labor rate in your area, the dollar amount shown should be correct. Tire rotation is generally included with another service type, (oil change, brake inspection, etc..) If you were to bring your vehicle into a shop for ONLY a tire rotation you may be quoted .5hr, which would make the dollar amount slightly higher.