You have every right to be confused by the poor wording....jeppessen really messed up big time there....
if you look again you will find "at or below" FL410....so the "climb or descend" 500 ft option was meant for the FLs below 410 but once you are at FL 410 then your only options are either descend 500 ft or climb 1000 ft....
To eliminate confusion just ask yourself what will your NEW altitude be after you initiate climb or descend?....if its going to be below 410 then use 500ft. and if above 410 then use 1000 ft.
Bear in mind that this procedure is aimed mainly at putting you on a FL that is separated from other aircraft on the same route, so, you will use the 500 ft when below FL410 (RVSM) because the normal separation is 1000 ft.
but once you consider going higher than FL410 (outside RVSM) then you use 1000 ft. because the normal separation is 2000 ft.
that's the whole trick there.....and also note that jeppessen are merely a provider for NAV publications and database, and they are prone to mistakes just like every one else, so if in doubt about anything, revert to the original publication that jeppessen used to copy the procedures (AIPs, AIRACS,ANNEX, etc.) because these publications always supersede Jeppessen.....