Scoring
Waste ratio
The cost unit of measure: evidenced idle spend as a proportion of total billed spend, converted to a penalty against a full score.
What it is
Evidenced waste divided by 30-day spend, both read from the account's own billing data.
How it becomes a score
The ratio is multiplied by a published penalty multiplier and subtracted from 100, bounded at 0 and 100. The multiplier is printed in the pack, so the arithmetic can be reproduced.
Why a proportion rather than an absolute
An absolute waste figure is meaningless without the spend it sits against. A thousand dollars of idle resource is a rounding error in one account and a serious finding in another.
The floor
Below 100 US dollars of observed spend the domain is not rated at all. Waste cannot be a meaningful proportion of a spend that small.
The null case
When every waste probe fails, waste is null and the domain is reported as not assessed rather than treated as zero waste, which would score full marks.
What it does not mean
It is not total possible savings. It is three classes of demonstrably idle resource, priced from your own billing.