Thanks. The key is not on the website deck plan but in the brochure. It might be helpful to put it on those. Thanks, A M Hughe.
I've just had a look at the deck plan in the med/baltic brochure and it explains the symbols in the bottom left corner of the page. + means 3rd/4th person occupancy available and triangle means 3rd person occupancy available. If there is just two of you then you may find the intrusion of the beds of the walls a bit of a nuisance so it may pay you to select one without these symbols which indicates a maximum of two in the cabin.