See the linked URL. Qqq still says that plural will be added when JavaScript supports.
Version: unspecified
Severity: normal
URL: https://gerrit.wikimedia.org/r/gitweb?p=mediawiki/extensions/LastModified.git;a=commitdiff;h=33a9b9a183c17812b804e630ea23bf660d2a5a62;hp=60a6573150fca7c4f6705d9f66b27e515761ee75