What is the meaning of "keeping nothing back but the bearings of the island"?

SQUIRE TRELAWNEY, Dr. Livesey, and the rest of these gentlemen having asked me to write down the whole particulars about Treasure Island, from the beginning to the end, keeping nothing back but the bearings of the island, and that only because there is still treasure not yet lifted. Dose it mean: You should tell... show more SQUIRE TRELAWNEY, Dr. Livesey, and the rest of these gentlemen having asked me to write down the whole particulars about Treasure Island, from the beginning to the end, keeping nothing back but the bearings of the island, and that only because there is still treasure not yet lifted.

Dose it mean: You should tell every detail about the island but you should not tell the exact location of the island?

This context is from a novel named: Treasure Island.
Thanks before hand.
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