The board
Who has been down there, and what they carried back out. Checked by your own computer, not by anybody else's.
There is no central board. Each node keeps the records of delves it was part
of and serves them at /board, so a board is what one machine
witnessed. Several can be merged: two people who were both there hold the same
delve with different signatures on it.
Nothing here is asserted. Your browser recomputes each address from the two public keys it was handed, verifies every signature against the bytes that were signed, and counts only what survives. If you disagree with a number here, you are right and the number is wrong.
Only delves with somebody else present and on air are counted. You cannot witness your own loot, and being reachable over the internet is not being somewhere.
What is counted
An address is derived from both halves of an identity, so a record cannot carry an invented signing key beside a real name: the address would not come out right, and the address is what the roster names.
A delve counts as cleared for you if the room was cleared, somebody else signed for it, and both of you were heard on air. Items are what you walked out carrying.
Anyone can publish a different board from a different set of records, and it would be no less true. This one is what one node witnessed.