H1B drop box visa appt india

If I am offered a H1B visa Dropbox appt for April 2023 in the online CGS system and don’t book it to wait and see if I get an earlier appt? Or if I don’t take the April 2023 appt. then afterwards the CGS will only offer me appts after April 2023?
I am asking if I have to book/take the first drop box appt offered or can I wait to see if an earlier appt slot may open? Or once I don’t take the first offered slot, the system will only show Dropbox appts after that date and won’t show me earlier appts if and when they open?