IAAL. From a legal perspective both the percentage of infringing activity matters, as well as the nature of the infringing activity.
Firstly, thanks to the ‘de minimis’ doctrine, small amounts of infringement do not count as ‘infringement’ in a number of jurisdictions.
Secondly, even if there’s copyright infringement, there are defences to it. These defences (whether in the form of the “fair use” doctrine, or in the form of specific “fair dealings”) both concern themselves with the amount of infringement as well as the purpose. If the amount is small and the purpose is, e.g., “transformative use” or if it falls under one of the recognized exceptions, then it doesn’t count as infringement. In India, for instance, under Section 51 of the Copyright Act, 1957, you are even allowed to import an infringing copy “of any work for the private and domestic use of the importer”.