Where did this number come from?
Board packs are assembled by hand, and every copy step quietly severs the link between a figure and the thing that justified it.
The board pack is the end of a long chain of copying.
A figure starts life in a model built by an analyst. It is pasted into a summary for a director. The director moves it into a slide. The slide is merged into a deck. The deck becomes a page in the pack. Every step is reasonable. Every step is also a small act of destruction, because what does not travel with the number is the reason it was that number.
The moment it matters
Nobody notices this until someone asks where a figure came from, and the honest answer is that somebody will have to go and find out.
That is not a trivial errand. Finding out means identifying who built the original model, whether they still work here, which version was current at the time, and what assumptions were in it. In practice the answer arrives days later with a caveat attached, or it does not arrive at all.
In an audit, that is a finding. In a board meeting, it is a credibility problem that attaches to the person presenting rather than to the process that failed them.
Why more careful copying does not fix it
The usual response is to tighten the process. Version control on the model. A source column in the summary. A rule that figures must be cited.
These help and they do not hold, for a straightforward reason: they depend on discipline at every step, by people under time pressure, at the exact moment when the deadline is closest. The pack gets assembled the night before. That is when the citations get dropped.
Anything that relies on people being careful under deadline pressure will fail under deadline pressure. This is not a criticism of the people.
What holds instead
The link between a figure and its justification has to be a property of the record rather than a habit of the person maintaining it. If the connection is made once, at the point the figure enters the system, then no amount of downstream assembly can sever it.
The test is simple and worth applying to your own last board pack. Pick any number on any page. Ask how long it would take to produce the document that justifies it.
If the answer is measured in minutes, the chain held. If it is measured in days, or in names of people you would have to ask, then what reached the board was a figure without a basis, and everyone in the room treated it as though it had one.