append time is the time AFTER THE BACKUP where a new backup job can append data. this is kinda counterintuitive.
an example:
let's assume your media set is append=2 days and overwrite=4 days
a media is used in a backup at 10 pm Monday and runs for 2 hours.
tuesdays backup at 10 pm will append to the same media.
wensday's will use it if it starts before 9:59:59 pm (2 days after the START of the job).
after that, it will not be overwritable until friday at midnight (4 days after the END of the job)
i hope this clears up your issue.
