April Doss, who served as senior minority counsel for the Russia investigation on the Senate Intelligence Committee and, prior to that, as a top attorney at the National Security Agency, said the S//OC//NF designation of the memo “seems like a typical level of classification for that kind of call.”
That classification indicates that the disclosure of the call would cause "serious damage" to national security, cannot be disseminated by anyone except the originator, and is prohibited from disclosure to foreign nationals. A code word classification, meanwhile, is top secret—a level higher than secret—and then further compartmentalized by adding a code word so that only those who have been cleared for each code word can see it.
Doss said it would be “highly unusual” for this kind of routine call between world leaders to be placed into a system that’s used for information about the nation’s most highly compartmented programs. “It risks undermining a whole host of important national security activities,” she said, noting that “most if not all” officials who would need to have access to call readouts as part of carrying out their regular duties in advising on foreign affairs and implementing the administration’s policies “would not have access” to the codeword system.