Ferry ticket in amalfi

Yes....but.... this is the Amalfi Coast where transportation chaos reigns. We never feared not getting on our timed ferry. In fact apparently any ferry would do. Here's an excerpt from a Trip Report I wrote on my 2 week stay in Sorrento in May 2023.

Let’s talk about ferries and chaos. On Monday we booked the early
Alilauro ferry to Amalfi with the intention when we got there to hop
on either the Travelmar ferry or SITA bus to Miniori. Except for the
boat to Capri, there’s no signage that shows what ferry is
arriving/leaving from which dock and you’re on your own to figure it
out. We found our dock, and the boat was there but it was deserted and
so we sat nearby to wait. Our ferry was leaving at 10:20 and the
competitor’s ferry-Caremar was leaving at 10:00. At about 9:55 there
was still nobody at our ferry to begin boarding and a guy with limited
English came over and gestured that the ferry was leaving. We showed
our tickets and gestured that we were on a different boat, finally in
English, he said the boat had changed and to get on. So, we hopped on
the Caremar ferry hoping we were doing the right thing. As we were
nearing Positano, OUR boat went speeding by, full of people and
arrived in Amalfi well before we did. We had watched this guy
intercepting many people and directing them to his boat and we have no
idea why, because there was no financial incentive as we hopped on and
off with no issues. On the way back, we befriended a bunch of Brits
waiting on the dock and they had the same experience, plus their
return tickets were for Caremar, but the time scheduled to leave was
the same as ours. We all hopped on the Alilauro boat, and nobody had
any issues.

On the day we went to Capri people were boarding the ferry we were on even when their ticket was for a different time. And they will pack you on shoulder to shoulder. I wouldn't worry.