Exactly as described, this flags whether this specific EMIX sequence was created by a user or generated automatically by the system at initialization, and per the description only user-created sequences can be edited. Attempting to modify a sequence that shows false here, meaning system-created, will be rejected regardless of what field is being changed, so this is the object to check first when a routine sequence edit unexpectedly fails rather than assuming a permissions or syntax problem. For example, one of the handful of factory-default EMIX sequences shipped with the firmware would show false here, explaining why an operator's attempt to change its letter pattern is rejected.