why is this red?

Can someone check that OSM and/or rails supports this plural?

it is being used in osm for the translations, in all the other languages as well.

This link is broken : This message supports plural. The different plural forms have to be prefixed as Rails plural forms, except for "other". See CLDR's Language Plural Rules for details on which forms may be applicable in your language. See Rails i18n on examples for adding Rails i18n basics.

http://github.com/avar/rails-i18n/tree/master/rails/locale/

where can i edit the text please?

I fixed the links to point to the rails i18n locale maintainer's GIT repository.