Specification
In short The specification is the value a supplier guarantees for every lot, for example at least 98%; UKPeps states none. The value actually measured is on the certificate of analysis for the lot, and it can fall on either side of a supplier's figure.
UKPeps does not guarantee a general minimum value. What counts is the value measured for each individual lot; it is published openly in the certificate library.
The difference from the measured value is the core of the term. The specification is a promise made in advance, for example at least ninety-eight per cent (UKPeps states none); the measured value is the result for a specific lot. Both belong on the page, and they belong apart, because they claim different things.
Besides purity, a specification usually states the appearance, the suitable solvent and the storage conditions. These details are the starting point for reconstitution, not the only option.
If a supplier changes its specification, the new promise applies only to lots tested afterwards. Older certificates are still to be judged against the specification that applied at the time.
Where UKPeps deliberately promises less than would be technically possible, and why, is explained on the quality page.