Bill,

I believe what you are referring to is called the "Principle of Reciprocity". In your example, when the hole is at MMC - 9.90, you have a positional tolerance of Ø0.05 - Therefore as the hole gets smaller, the unused positional tolerance is lost. As toleranced, any holes smaller than 9.90 are not acceptable.
The Principle of Reciprocity states that as a hole departs from it's maximum material condition (i.e. gets smaller), any left over positional tolerance may be used in a directly proportional manner. This often notated as Position|Tolerance (circle M) (circle R)|Datum Reference(s)
The same thing can be achieved by using a Ø0.0 positional tolerance on the hole like this: hole size 9.85+.25/-.00 Position Ø0.0.
This table may explain better:

ActualSize.|.Pos.Tol.MMC..|.Pos.Tol.MMC/Rec.
of Hole....|.Ø0.05 M......|.Ø0.05 MR

8.85.......|.not allowed..|..Ø0.00
8.86.......|.not allowed..|..Ø0.01
8.87.......|.not allowed..|..Ø0.02
8.88.......|.not allowed..|..Ø0.03
8.89.......|.not allowed..|..Ø0.04
8.90.......|.Ø0.05........|..Ø0.05
8.91.......|.Ø0.06........|..Ø0.06
. . .
9.10.......|.Ø0.25........|..Ø0.25


Lowell Foster (Chairman of the ASME Y14 subcommittee #5 on GD&T) writes in his book "Geo-Metrics III , The Application of GD&T Techniques" (1994 Addison Wesley Longman), "The principle of reciprocity is perhaps the most advantageous method of specifying position tolerances to mating holes or pins which recognizes, and utilizes, the interplay and interdependace of allowable location and size tolerances."

The principle of reciprocity is not included in the USA standards, but is proposed for addition to he ISO standard ISO 2692, Maximum Material Requirement. It was proposed for inclusion in the ISO Standard around 1971, but was considered too advanced. Mr. Matsumoto of Japan also put forth this Idea around that time and described it as the "Extreme Position Method", and suggested the symbol "circle E".

I Hope this help's - I would be happy to scan an the excerpt from Mr. Foster's book for anyone to read.

-Keith Walter
Manager, Quality/Lead CMM Programer
Devonshire Manufacturing Inc