Every burial site the jIA created has a standard location measurement using military and engineering trigram. They used that for them to recover all by only using a single reference point although they created plenty of surface signs to as supports or reserve sign if ever those other signs unable to survive for a long time. That is why they created different kind of surface signs and classify them, creek, falls, hill, rivers, creeks, old road, railroad, each corners. Main signs and supporting signs, directional signs and trail signs, tree rocks muhon or boundary post. Did you know that those planted trees were classified in accordance to the load that the tree is representing? There are proof about all of these, if you heard of a story about a Japanese hunter just looked at the sunrise and walk several steps then got the location of load instantly that is a triangulation method which is the most accurate way than using a gadget. That is te reason why Marcos recovered a lot by employing true Japanese readers and those Japs trained few Filipinos which some of those trained Filipinos surviving up to present day.They did hunting in a very easy way because surface signs are still available. So read the books but do what is right.
Anyway forget about that surface sign topic. Your dig site is promising but you are probably at the second level load lying at 55 to 65 feet. The square sign is telling you that the first load was missed.
Another tricks the Japanese engineers put on the signs. Some rocks that you found are also infos regarding loads with same level but are separated about 25 to 50 meters away, expert Japanese sign readers know that. Some rocks are clustered and shapes are repetition but the meaning actually are direction in accordance to compass reading.
I have read so many books and code books online but i doubt about some of the meaning written in there. There are secret message in every signs.
Well, regarding your dig site, you are about to succeed. In tagalog word "abot kamay na". Good luck.
Happy hunting!