Examiner can provide not more than quarter of the training 
If you are an examiner providing the training towards the license, rating or certificate you are not allowed to provide more than 25% of the overall training.
FCL.1005(a) hard law saying - an examiners shall not conduct skill tests or assessments of competence of applicants for the issue of a licence, rating or certificate to whom they have provided more than 25 % of the required flight instruction for the licence, rating or certificate for which the skill test or assessment of competence is being taken.