Which one is the correct expression?

[sabonis]

I use Rosetta Stone to learn Spanish, first I was using Latin America version, but now switched to Spain version, since I live in Europe. There are a few differences but one of them really bugs me:

In Latin America version it says: Nosotras somos ninas
In Spain version, it says: Nosotras somos unas ninas
or
In Latin America version it says: Nosotras tenemos bicicletas verdes.
In Spain version, it says: Nosotras tenemos unas bicicletas verdes.

The extra "unas" really bugs me, it seems to me that it is redundant/unnecessary. Eventhough I don't know Spanish, it doesn't seem right to me, to use that extra "unas".

Which one should I use?