oneThis plural form is used for numbers like: 1
You have <%= count %> unread notification
otherThis plural form is used for numbers like: everything else
You have <%= count %> unread notifications
You have <%= count %> unread notification
You have <%= count %> unread notifications
<%= count %> 件、未読の通知があります
You have <%= count %> unread notification
You have <%= count %> unread notifications
<%= count %> 件、未読の通知があります
You have <%= count %> unread notification
You have <%= count %> unread notifications