If the PM is making their own assessment then it needs to be in enough detail to convince the Contractor that it is correct, otherwise they are more likely to want to take the matter to adjudication.
NEC4 practice note 1 and the new wording of 63.5 (Jan 2019 amendments) make it clear that you assess a compensation event against the last Accepted Programme BUT only after taking into account progress and other compensation events that occurred before the date the compensation event was instructed/notified (known in NEC4 as the dividing date) . The principle of this guidance note is still applicable to NEC3.
NEC4 practice note 1 and the new wording of 63.5 (Jan 2019 amendments) make it clear that you assess a compensation event against the last Accepted Programme BUT only after taking into account progress and other compensation events that occurred before the date the compensation event was instructed/notified (known in NEC4 as the dividing date) . The principle of this guidance note is still applicable to NEC3.