مَّرْقُومٌ (inscribed): It is derived from the Arabic word الرقم (The writing and engraving on stone), meaning, it is a Book in which the deeds are recorded in a way similar to a fixed engraving that is permanent. It is documented, not erasable. Or,
مَّرْقُومٌ (known): It is known to its owner. So, the Book of the wicked is marked with the characteristics of the wicked, so this Book is so documented and precise that disclaim any suspicion of forgery, adding or omitting because the writers are the noble angels who know what you do.