Thread:MediaWiki talk:File-info/Where is $1 coming from?

This message and a few others similar to it (mediawiki:file-info-size, mediawiki:file-info-size-pages, mediawiki:fileduplicatesearch-info) receives an argument (here $1, for the others it is usually $3) which unfortunately is not a pure number, but a number with a unit symbol. The symbol is wrong: sizes in kibibytes (binary powers such as 1024, etc.) use the kilobyte symbol. Where is this error being injected in?