There is relaxation in the age limit for candidates with a benchmark disability in the BPSC (Bihar Public Service Commission) exam. The details of the relaxation are as follows:

General Category:
- The maximum age limit for general category candidates is usually 37 years.
- However, candidates with a benchmark disability are given a relaxation of 10 years in the upper age limit.
- This means that the maximum age limit for general category candidates with a benchmark disability is 47 years.

OBC Category:
- The maximum age limit for OBC (Other Backward Classes) category candidates is usually 40 years.
- Candidates with a benchmark disability in the OBC category are given a relaxation of 10 years in the upper age limit.
- This means that the maximum age limit for OBC category candidates with a benchmark disability is 50 years.

SC/ST Category:
- The maximum age limit for SC/ST (Scheduled Caste/Scheduled Tribe) category candidates is usually 42 years.
- Candidates with a benchmark disability in the SC/ST category are given a relaxation of 10 years in the upper age limit.
- This means that the maximum age limit for SC/ST category candidates with a benchmark disability is 52 years.

It is important to note that the benchmark disability should be certified by the appropriate authority as per the rules and regulations set by the government. The candidates need to provide the necessary documents and certificates to avail the age relaxation.

Summary:
- General category candidates with a benchmark disability have a maximum age limit of 47 years.
- OBC category candidates with a benchmark disability have a maximum age limit of 50 years.
- SC/ST category candidates with a benchmark disability have a maximum age limit of 52 years.
- The benchmark disability needs to be certified by the appropriate authority and candidates need to provide the necessary documents for availing the age relaxation.