Hello @Lauren285,
The special offer button shows up at the start only for reservation inquiries. It doesn't show for reservation requests. For requests you have the option to accept or decline. For inquiries you'll see the option to pre-approve or decline.
The difference between inquiries and requests is explained in the article below.
Difference-between-a-Reservation-Inquiry-or-Request-A-Community-Help-Guide
When a guest sends a reservation request they're ready to commit to book at the advertised price whereas when they send an inquiry they're not yet ready to book as they may have some questions so having the ability to send a special offer may entice them to send a reservation request in this case.
If someone has sent a request and then wants to change the number of guests either you or they can send a change request. You can go to their reservation, click "change or cancel" and follow the process to change the number of guests. The guest must then accept the change for it to come into effect.
Steve.