How much jerking do you have to do before you call it a tonic-clonic seizure?

Tonic-clonic jerks. A brief seizure with jerking only for a few seconds can still be a tonic-clonic seizure. To know you need to have an experienced observer who has seen one before. There is no way you can identify this yourself (since you would be unconscious). Other indications that a tonic-clonic seizure occurred include: biting your tongue, wetting yourself, a vertebral fracture, or gasping for breath afterwards.
More than one more t. A single jerk would be called a myoclonic jerk characterizing myoclonic seizure.