Uneven fractional digits break the point of a vertical comparison

What it is

In one column, some values carry two fractional digits and some are written as integers. The decimal mark then leaves the shared vertical, and 10 cannot be compared with 10.50 by position. Consistent fractional digits is a format demand from the comparison: if the column is for comparing, treat the mark as an axis, pad the places, and hold empty places with zeroes or a tabular blank.

Why it happens

The decimal mark is the anchor where integers become fractions. A vertical comparison finds that anchor first, then reads both sides. Ragged precision lets the anchor wander; a units digit on an integer row may sit under another row’s tenths, and format has swapped magnitude. Money columns show it clearly: some systems drop fractions on whole amounts, others always keep two places, and mixed in one column they look like two ledgers. Percents and scientific values do the same — 12% beside 12.0% can line up the sign while the significant digits do not. Padding with zeroes is not a claim of extra precision; it fills the cells. If precision truly differs, split the column or mark significant figures, rather than omitting fractions to look tidy.

Where it stops holding

A totals row at a coarser precision than the details is an accounting habit (cents in the lines, units in the total). Separate that row visually; do not pretend it shares the axis. Missing or not-yet-computed cells must not become 0.00 just to pad — that is fake data. Use a blank or a dash, and do not make the dash sit on the decimal axis. Dots in non-comparison strings (timecodes, firmware 1.0.3) are not decimal marks and should not be padded. Locales differ on comma versus point as the mark; what must be consistent is each place’s role in the column, not which glyph is used.

Applying it

• Agree fractional digits for a comparison column and pad on render, with zeroes or a tabular blank. Do not paint however many places the raw value happened to have.
• Drop 10, 10.5, and 10.50 into one column and look at the mark. If it jumps, the comparison has already failed; do not start by bolding the maximum.
• Give a coarser total its own row and style so it does not fight the detail axis.

Related

• Same group: F4.18.1 Table numbers need tabular figures or the column will not line up · F4.18.2 Money and serials should sit on the trailing edge so places can be compared · F4.18.4 Space and wrapping between a number and its unit need their own rules
• Nearby: E4.03 Tables · U3.01 Numeric axes
• Search terms: decimal alignment · fractional digits · numeric precision