Take a look at:
siteSettingRate: I18n.t('logs_error_rate_notice.rate', { count: siteSettingLimit, duration: duration }),
And the translation:
rate: one: "1 error/%{duration}" other: "%{count} errors/%{duration}"
How can the translation system choose the plural form? It should check the variable, but which one?
Here comes that “count” is always used as the “plural variable” that the system depends on when choosing the forms.