A user found these issues:
1. Option "k" not explained:
section SYNOPSIS, second line:
at [-V] [-q x] [-f file] [-u username] [-mMlbv] timespec ...
at [-V] [-q queue] [-f file] [-u username] [-mMkv] [-t time]
the option "k" has to be removed.
2. Tasks in the past.
The man page says that "If you specify a job to absolutely run at a
specific time and date in the past, the job will run as soon as
possible. For example, if it is 8pm and you do a at 6pm today, it will
run more likely at 8:05pm."
However, it is more likely that you get: "refusing to create job
destined in the past".
Papoteur