Each record is a transcription from the British Library's catalogue. The amount of information listed varies, but the records usually include the following information about your ancestor:
This is an index of naval officers who served in India. The Indian Navy Service Statements at the British Library cover European and Eurasian personnel, and include not only regular officers but also warrant and petty officers, clerks, engineers and other ranks. The records relate mainly to men serving in HM Indian Marine and its successors (up to 1947) but, where appropriate, they also give details of an officer's previous service in the non-combatant Bombay Marine and in the pre-1863 Indian Navy.
The collection includes the British Library reference giving the volume and entry number for each service statement. For example, the reference given for J. Cowlishaw is IOR/L/MIL/16/1/163-64. This means that his statement is entry 163-64 in the volume IOR/L/MIL/16/1.
Once you have identified an individual in this index, you can order copies of the statement from the British Library online. Alternatively you can arrange to visit the British Library to see the record in person.