Values and Tolerances

Whatever the chart prints at, on or beside the mark is the value, in full:

• 25 (13.0%) stays 25 (13.0%) — not 25, not 13.0%, and never 25 countries (13.0%);
• printed formats stay: thousands separators (11,270), decimal commas (2,08), currency and percent marks, parentheses for negatives (($60B)), footnote markers (<sup>1,2</sup>3.60);
• printed beats geometry: where the label says 43, the value is 43 even if the bar top measures a hair lower.

Where nothing is printed, the value is read at the mark's visual centre against its own axis — a second axis where the series is scaled by one (see Dual-Axis and Combo Charts (§11.2.2)), the decade bands of a logarithmic axis (see Log Scale Charts (§11.2.6)), and a stacked segment's own two boundaries (see Stacked Bars and Waterfalls (§11.2.9)).

An estimate SHOULD be a value a careful reader could defend within the readability tolerance below — neither falsely precise nor coarser than the axis allows.

How an estimated value is written. An estimated value MUST be written as a bare number in the axis's own format — its unit mark (2.5% on a percent axis) and its digit grouping (17 000 on an axis ticked 18 000) — with no approximation marker, and no more precise than the reading supports: at most one decimal place beyond the axis's tick labels, and two significant figures on a logarithmic axis. Whether a value was printed or estimated is recoverable from the page and is not marked in the Markdown.

A mark drawn at the baseline is 0. A labeled position with no mark at all is also 0 — the histogram's empty 1500 bin is 0 (see Bars and Histograms (§11.2.1)). A stack that simply has no segment of one series leaves that cell empty instead (see Stacked Bars and Waterfalls (§11.2.9)).

A printed bar value is copied first. Otherwise the value-bearing edge is read against the corresponding axis plane, excluding perspective depth. Where the reference plane is ambiguous, the value is the midpoint of the plausible readings.

A checker compares each cell with the value it reads off the page:

• Printed value — the same number, compared exactly. Formatting variants of the same number (thousands separators, decimal comma or point, currency and percent marks) MAY be treated as equal; a different number is wrong.
• Estimated value — accepted within a relative tolerance of the checker's own reading, chosen by how readable the mark is:

Most estimates fall between 0.05 and 0.15, and a tolerance above 0.2 is exceptional. The tolerance is the range a careful eye can defend: not so tight that a second careful reading fails it, not so loose that a wrong reading passes. For bars drawn in perspective it is widened to cover every plausible reading.