how old are the files/directories? they could be left over from a crashed appserver, or something else...
does the blcli Delete cleanupAllAppServerCaches do anything?
if not, you can likely stop the appserver, delete the files in the directory and restart, though check w/ support if there are files you should not clean out...
there are files and dirs for every single day since the appserver was installed
cleanupAppServerCache is running every night
i will contact support