What are close to money contracts?

When Options expire, both in case of STT and now in case of physical delivery, Close to money or CTM contracts have an option of do not exercise. What contracts are considered as close to money?

As per this NSE circular

The CTM strikes range shall be arrived as under:

  1. For Call Options - 3 ITM options strikes immediately below the final settlement price shall be considered as ‘CTM’

  2. For Put Options - 3 ITM options strikes immediately above the final settlement price shall be considered as ‘CTM’.