Section 2.4.1.3.1, “Technical Features that Incorrectly Define an Invention,” of Chapter 1 of Part 2 of the Patent Examination Guidelines provides the following two examples of indefinite descriptions: (1) “For example, for a composition defined by a close-ended transitional phrase, the sum of the upper limit value of a certain component of the composition and the lower limit values of other components exceeds 100%”; and (2) “Another example is a composition defined by a close-ended transitional phrase, where the sum of the lower limit value of a certain component of the composition and the upper limit values of other components is less than 100%.” The description “defined by a close-ended transitional phrase” is exemplified by the close-ended transitional phrase “consisting of” in the examples. However, these examples merely serve as illustrations and do not mean that it is not necessary to determine whether the content percentage of a component in a composition defined by an open-ended transitional phrase is definite.

Principles for determining whether the content percentage of a component defined by an open-ended transitional phrase is definite:

(a) Regardless whether a composition is defined by an open or close-ended transitional phrase in a claim, if the sum of the upper limit of one component and the lower limits of other components exceeds 100%, the claim would be deemed indefinite.

(b) For a composition defined by an open-ended transitional phrase in a claim, if the sum of the lower limit of one component and the upper limits of other components is less than 100%, the composition may still comprise other components that are not recited in the claim, such that the total content may reach 100%. In that case, the claim would be deemed definite.

For further details of this supplementary clarification, please refer to the TIPO’s website. (https://www.tipo.gov.tw/tw/cp-85-985669-eacb6-1.html)