I can't yet book a July 16 train from Copenhagen to Svendborg (where we will get on the ferry to go to Aero Island.) The booking calendar only seems to go out 60 days, instead of the 90 days that is so common in other countries. So I need to wait about another week.
To get an idea of what the tickets might cost, I picked some random other dates. If we were traveling on May 31 and wanted to arrive in Svendborg at the time we've picked (around 3:00), the total journey would take 2 hours 43 minutes and "orange tickets" are available for 25 dkk. The "orange" tickets are their buy-early mini price tickets that cannot be modified after purchase, and they do sell out. The standard ticket for that same departure time is 309 dkk. That's a big price difference so I do want to try to get the orange tickets. For the period of June 22 to June 29, the trip only takes 2 hours 3 minutes and orange tickets are available for 97 dkk (except on one date in that range that shows the orange price tickets to be 193 dkk). For the period of June 30 to July 8, the trip (with the departure time that I picked) takes 2 hours 34 minutes and the only price shown is the standard price of $309 dkk.
Why are there no orange ticket options for dates in the range of June 30 to July 8? Is this because the orange tickets aren't offered during high season? Or is it more likely because the orange tickets have already sold out for the June 30 to July 8 dates?