Both are also logged as MULTI-PILOT TIME
How can you log multi pilot time when you haven't got a rating for the aircraft you are flying? The short answer is you can't.
If you want to keep a log of these hours for the purposes of ATPL licence issue at a later date then put them into a "memo" column and make sure that they don't add across into your flying hours - be they single or multi pilot. You can put something constructive in the remarks section beside the hours as well in order to make the CAA's life easier when they review your logbook later on.