The natural interpretation of the expression "dispensing set" is a set of equipment (a series of instruments or devices) designed for dispensing something. However, the real meaning in this case turns out to be different.

This apparatus, the Dilumat S®, is a diluter designed for laboratory analysis. The user introduces a sample of a solid or semi-solid substance into the machine, the machine automatically weighs it and dilutes it, dispensing (supplying or administering) exactly the right amount of diluent to achieve the required degree of dilution.

The apparatus is French; it is made by AES Chemunex. The manual is bilingual, in French and English, and I think it is clear that the English version, which includes the expression "dispensing set", is translated from the French.

"Dispensing" is a translation of "dosage", meaning the measurement and administration of a certain quantity of diluent. The expression "dispensing set" occurs in the definition of parameter no. 14 in the "Dispensing report" ("Rapport de dosage"). In French it appears as follows:
"14- Set weight (g): Masse de dosage programmée en grammes"
And in English:
"14- Set weight (g): Weight of the dispensing set in grams"

So "dispensing set" corresponds to "dosage programmée", in other words, the weight in grams of diluent set or programmed by the apparatus, according to the weight of the sample and the degree of dilution required.

http://www.innovationdiagnostics.com/User_Manual/Microbiolog... , p. 52

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Note added at 4 hrs (2011-12-25 10:47:55 GMT)
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The reason why this phrase is obscure is that "dispensing" is being used here to mean "amount (to be) dispensed", which is not really correct usage in English.

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Note added at 7 hrs (2011-12-25 13:08:13 GMT)
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Excuse my error in French; I said that "dispensing set" corresponds to "dosage programmée", but if that were accurate it would be "dosage programmé", since "dosage" is masculine. In fact, the expression is "weight of the dispensing set", corresponding to "masse de dosage programmée"; "programmée" applies to "masse", not to "dosage". So "set" is an adjective qualifying "weight": that which is established or prescribed is the weight (more accurately the mass) of diluent dispensed.