It does mean rest, but in this case, Lorena was on the right track, it is temporary disability leave.
I was mistaken to assume that "CT" meant under medical supervision in this case. It is short for "continuar trabajando" (of course!), as the second link below makes clear. The first link below specifies that under the PR'n system a worker can either receive medical treatment while "CT" or in "Descanso" --either working or on disability leave.
(The document Lorena linked to also helped by providing the definition of "dietas" in the CSFE system which I needed.)
http://www.transicion.pr.gov/2012/070/Informe de reglamentos...http://www.jp.gobierno.pr/Portal_JP/Portals/0/Informate/Comu...