I mistakenly added 5 oz of Chocolate Extract at the beginning of secondary instead of the day before bottling. Still smells ok, when I did some quick checks, but wondering if anyone else has made this mistake and what the results were. This is a Chocolate Milk Stout. Thanks.
You're perfectly fine. If the extract has sugar in it, it means it will ferment out, which is safer to do during secondary than at bottling anyways. If not, it just means it will have more time to naturally mix in to the beer during secondary, as opposed to having to stir it in at bottling time.
For any sugarless extract addition, you should be able to add it at whatever time (after primary fermentation has completed). The biggest advantage to doing it earlier as opposed to later is to allow it to naturally mix as opposed to having to stir.