Whole numbers
The first rule is about meaning, not precision. A call either happened or it didn’t, so
23.1 calls describes nothing that exists. Apply it to any object that cannot be
partial — calls, contacts, users, campaigns. It does not apply to averages and rates,
where a fraction is the point.
Abbreviations
When to abbreviate versus show the full comma-separated number conflicts with the rule
above, and the source does not resolve it — see
Open issues for the proposed reading and
why it’s still an open question.
The source states the fourth rule as “If amount is a whole thousand, such as $1,000, do
not show a 0 decimal” while illustrating it with
12M / 12.0M. The description and
the example disagree. The rule that is actually being expressed — and the one both
examples support — is: never render a trailing .0. That is what is documented here.Percentages
Same precision rule as abbreviated numbers: one decimal, and never a trailing
.0.
Currency
Currency is the one case that takes two decimal places rather than one. Cents are a
real denomination; a third digit is not. This is why the one-decimal rule elsewhere on
this page does not apply here.
Constraints
Gaps in the current rules
Numbers: open issues
Divergences, open decisions, and undocumented gaps for Numbers.
Why it works this way
One decimal place everywhere except currency. An abbreviated number is already an approximation —2.77M presents two digits of precision on a value that just discarded
five. One decimal signals “roughly this much” while still distinguishing 2.7M from
2.9M. Currency is exempt because cents are an actual denomination someone can be billed.
Trailing .0 is never rendered because it is a claim about measurement. 12.0M
reads as “measured to the nearest hundred thousand.” 12M reads as “about twelve
million,” which is what the abbreviation means.
Uppercase K and M — lowercase m is the SI symbol for milli, three orders of
magnitude in the wrong direction. The uppercase form is unambiguous in a product where
numbers appear next to units.