Under normal circumstances, colleges and universities will publish specific vacancies on their own campus networks and the websites of provincial examination institutes, and some places will also publish them in newspapers.
Under normal circumstances, the supplementary record will be lower than the normal admission score, but individual phenomena are not excluded. When registering, you should generally refer to the admission scores of various schools in previous years.
The time for re-recording is generally within one or two days after the admission of each batch. According to what you said, the second batch of admissions in your province is not over yet, so the re-recording work should not have started yet. You need to pay attention to the website of the provincial examination institute, the local newspaper and the notice of your high school in time to avoid missing the re-recording time. Different provinces have different registration methods, but at present, most provinces register online through the website of the Provincial Examinations Institute, or register at the Provincial Examinations Institute through the high school where the candidates are located.
Because I am not in the same province as you, what I said may be different from the local situation. It is a sloppy thing to register for the college entrance examination. You still have to be more careful. I wish you to be the first.