I believe it would come to "keeping in specification", in about everything produced.
For instance, lets take .284 as the needed diameter but the spec. may be .284 +/- .002.
So the item can be .282 to .286 and still be acceptable.

Another instance would be bullet wght., lets say 160 grains but if you weight a number of bullets
you will find a variation of say +/- 001 grain but all meet the spec.

Let us suppose you have a barrel at .282 and a bullet at .286 you might get some excessive pressure
but unless you are a target shooter it won't matter much.

Just to add the Cdn.280 Ross which still has a following mostly in Europe has a spec. of .287 bullet
dia. This may be the confusion.

FWIW --- John