Non-PRO Norwegian to English Other Certificates, Diplomas, Licenses, CVs Grade appearing on a transcript

Not much to go on here... I have a transcript of grades/scores for a Norwegian secondary school and the abbreviation "DT" appears among the scores, and specifically (and only) for "Norsk sidemal, skriftlig."

While the phrase "daglig tale" comes to mind, it doesn't really fit in as a grade or score, though I suppose it could be simply a comment or note. The transcript's glossary does not contain this particular abbreviation either.

Probably the simplest thing, but it's not coming to mind. Any ideas?