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Yeah and besides documenting the parameter it should also be used in English. Not just because per the reason mentioned by Purodha, but because the English text is also incorrect in case of 1.

I submitted patch which add plural support. I see no need to change the current English text to use singular form though.

Is "1 Translations/month" correct?

It's not a sentence.

Then what it is?

You can think it as Measuring instrument which is part of the Page layout.

That it is but from different POV than the one being considered.