Prolific will only ever recruit the number of participants that you have requested when you set up your study. If you check in your submissions list you should have only the total number of submissions you requested awaiting payments or approved (i.e., in 'awaiting review' or 'approved' status).
Submissions that have the status 'timed out' or 'returned' do not count towards your total number of submissions and do not require any further action. Therefore, even though you may have more submissions in your submission list than originally requested, it is likely that this is because a participant has 'timed out' or 'returned' and then another participant has been automatically recruited to take their place.
However, if you have manually approved any 'timed out' or 'returned' submissions at the end of your data collection then these submissions will be considered extra to the number originally requested.
This will therefore result in you having more approved submissions in your list than you originally wanted.