[Localization] Plural forms of strings

I don't know the proper terms for this, so I will just explain it simply. I've been translating and noticed string Trash contains %d items doesn't have multiple plural forms (for 2,3,... items). I'm used to translations having msgstr[0],msgstr[1],msgstr[2]... for this (like in Thunar). Please update the strings (or merge? into one) Trash contains one item Trash contains %d items

Also let me know what is the correct wording for this problem, so I can explain it better in the future. Thank you :)