This is a nightmare topic.
I use K for targeted support – 3 or more interventions OR any external eg SALT, advisory teachers, OT, Physio etc
Otherwise they are N BUT I separately keep a track on my whole school provision map and I mark anyone below K as having access to universally available provision mapping.
I found if I include everyone that has anything at all, I was getting up to 68% SEN in some (mixed ability) classes.