In T 2017/07 the board stated that a composition which is specified in a claim to comprise a component in an amount which is defined by a numerical range of values is characterised by the feature which requires the presence of the component within that range, as well as by the implicit proviso which excludes the presence of that component in an amount outside of that range. Consequently, the amount of that component present in the composition must not exceed the upper limit of the numerical range indicated. An amendment restricting the breadth of that component, for instance by narrowing down a generic class or a list of chemical compounds defining that component, has the consequence of no longer requiring the presence within that numerical range of those chemical compounds no longer encompassed by the restricted definition of that component and, thus, of limiting the scope of this implicit proviso. A composition which is defined as comprising the components indicated in the claim is open to the presence of any further components, unless otherwise specified. Thus, in a claim directed to an openly defined composition, the restriction of the breadth of a component present therein may have the effect of broadening the scope of protection of that claim, with the consequence that in opposition/appeal proceedings such amended claim may extend the protection conferred by the granted patent (Art. 123(3) EPC).

With reference to T 2017/07, the board in T 9/10 held that the use of the term "comprising" in connection with a numerical range defining the amount of a component implicitly meant that the protection conferred by the claim did not extend to compositions containing that component in amounts outside the defined range.

In T 999/10 the board considered that sequential drafting (formulation "en cascade") in an open claim ("comprising"), i.e. retaining in an amended claim the broad definition of claim 1 and adding, by means of the expression "and in which ...", an additional limitation, avoided the situation contemplated in T 2017/07, where an amendment initially made with a view to limiting a claim in fact extended the scope of protection it conferred (Art. 123(3) EPC).

In T 1360/11 the board confirmed that in a case where a granted claim, directed to a composition defined in an open manner and including the presence of a component belonging to a class or list of compounds in a quantity defined by a range, was later amended by limiting the definition of the class or list of compounds, in spite of the apparent limitation, the wording of the granted and amended claims might be such that the amendment results in an extension of the protection conferred contrary to the requirements of Art. 123(3) EPC. The problem was well known in the case law, see e.g. T 172/07, T 2017/07, T 832/08, T 1312/08, T 869/10, T 287/11. The board observed that by means of inserting a double condition the claim may not extend the protection conferred by the patent. A possible infringement of the requirements of Art. 123(3) EPC might be avoided by including in the amended claim a quantitative condition on the limited class or list of compounds and an additional constraint on the total amount of compounds belonging to the broader class or list. See also T 514/14 and T 1063/15.

In T 491/13 the board distinguished the case at issue from the above cited cases, since it did not relate to a restriction from a list of compounds comprising one or more of said compounds (here the solvent) or a mixture thereof, or to a list defined broadly as a general chemical class or a broad chemical formula. In addition, the situation also did not apply to the case at issue, since the protection conferred by claim 1 as granted extended to compositions containing the selected component in amounts inside the defined range and potentially one or more supplementary unselected compounds in any range.

In T 306/14 the board considered that a possible way out of the situation was a sequential drafting of the claim (formulation "en cascade" as in T 999/10). Alternatively, T 1360/11 held that the result of amending the claim by inserting a "double condition" was that the claim did not extend the protection conferred by the patent. In the case in hand, the appellant had chosen the second possibility and amended the claim by including a further limitation of the total amount of the milled filler (double condition). The board agreed with the respondent/opponent that the claims were not identical to the claims in decision T 1360/11, wherein the added condition also specified the amount of the specific components, but the idea was exactly the same. Adding the second condition ensured that the total amount of milled filler remained within the scope of the granted claims.