For most conferences, there is an informal grey area in the submission deadline. The conference typically states that nothing will be accepted after hour X on date Y in timezone Z, but often the system doesn't actually shut down submission at that time, but a little while later. This may be for any number of reasons, frequently including:
- Giving a grace period for technical problems or slow uploads
- Supporting extensions that have been requested by and granted to particular authors
- Just plain not seeing any reason to bother with precision
From my experience, the most important driver for all of this sloppiness about time is that the point of the submission deadline is not so much to stop submissions as to enable a fair and well-organized peer review process to start in a timely manner. Thus, as long as the submissions are shut down fairly promptly after the deadline and review assignments can be sent out on schedule, nobody really cares all that much about timestamps: there's nothing magic about 11:59pm in American Samoa. Likewise for a camera-ready / revision deadline: the point is not to stop submissions but to allow publication to begin.
As such, I see no issue with what you have done. The formal deadline is the point after which you have no grounds to complain if you can't change anything any more. If you happen to notice a further correction to make and the system is still accepting them, well, that makes things better for everybody, and it's likely the organizers won't even bother noticing, let alone be unhappy that you did so if they do notice.
Now, it's possible that you might run into a program chair who is unusually dedicated to precision and does not share this opinion, but I have never yet encountered such a person in my professional life.