Every form that starts with an "S" is related to....you guessed it: "Service" it goes to a specific section of the Service Department of every Branch. The S-10 is just a bunch of statistics, averages of hours, mags placed, average attendances at the KH. It does not evaluate elders or even ministerial servants. It also repeats the personal data of the Coordinating Overseer (former Presiding Overseer) and the Secretary. Nothing sexy there.
If something "hot" comes up or a Elder or MS has to be reevaluated, the CO will go into great lenghts to do an extra letter, where he describes and writes a text about said "situation". It can be from totally boring like
"Brother Pisserson has severe problems in the congregation, because his service averages are below 10 hours and he is also not conducting his family study every Monday."
To outright red-flashing-light-district-descriptions like:
"Brother SexyClassy slowly pushed her G-string down to reveal....."
Usually they are advised to not write "too graphically" but not all follow "the instructions" ....