Hello Gibson,
The first part of your query is entirely a local matter. It is you (your company) who decides the definition or Demarcation of a repair to be Breakdown or not depending on various aspects like Criticality of the Equipment, Duration of the Breakdown etc. For example, companies have their equipments categorized into A, B, C categories. a being the most critical. Further they decide like:
1.Any unplanned repair on A category will be treated as Breakdown.
2.An unplanned repair on B category Equipment will be Breakdown when the duration crosses certain limit 9say 30 minutes or 1Hr)
and similarly for other categories.
The second part
When you decide this, you will be giving a Breakdown Tick in the Malfunction notification for all such qualified Repairs. You will get MTTR and MTBF reports only for those Notifications where this tick is there. As per the definitions of MTTR and MTBR, for effective Equipments MTTR needs to be less and MTBR needs to be more.
See these useful posts
What are the prerequisite for getting MTTR / MTBR data.
MTTR / MTBR / Breakdown Analysis Information System Overview
Equipment Availability - Concept & Issues
Also SAP note 80311.
KJogeswaraRao