We want to take the ferry from Turku to Stockholm on 20th of June, the night ferry. We emailed with Tallink Silja, and they informed us we have to use the "interrail" code to get the discount. So we tried, and it did gave us a discount, but not 50%. After another email, we now got this answer:
"20.06 20:15 is a high season (red) departure and therefore the discount is 30%.
50% is only on low season (green) departures."
At the official interrail website, there is no mention of a difference in discount between high and low season. Which is the official discount we should get? Do the companies have a contract with interrail, or can they adjust the discounts as they like? We would want to book the ferry in advance, to be sure to have a cabin space for the night ferry, but off course if we can't get the discount online we might try to book when we are in Finland (we are there from 15th of June, so 5 days beforehand, but in Tampere not Turku).