Past perfect tense with Andare

In Level 1 module 5.9: Past Tense -Imperfect it states the following in the exercises:
-Loro sono andati
They went (feminine)
-Loro sono andate
You went (formal plural -not commonly used).

I thought "Loro sono andati" should be "andate" if feminine, and "Loro sono andate" should be "andati" if in the formal plural form. 

Am I wrong?

Ciao Riccardo, 

Thanks for your question!

Indeed there is a mistake in the lesson, which we are going to fix right now (thanks so much for flagging it!).

Just to clarify and confirm what you correctly pointed out:

• "loro sono andati" means "they went (masculine)"
• "loro sono andate" means "they went (feminine)"

The sentences "Loro sono andati" (masc.) and "Loro sono andate" (fem.) could also be used in a formal plural You form but it's extremely rare.

Hope this helps! :)

Grazie Davvero.