Beginner Debsecan Question

[GregTomkins]

Apologies if I am in the wrong place. I'm somewhat new to Debian and experimenting with debsecan;

- ran 'apt-get install $(debsecan --suite jessie --format packages --only-fixed) ', no obvious errors

- ran 'debsecan --only-fixed --suite jessie', there are still a few dozen items, all marked '(fixed)'.

After updating, I was expecting to see that no fixes are outstanding. Why don't I?