What's in the Name?

I got some seeds and on the envelope it said:
Salvia sp.  

Salvia officinalis = Sage with herbal uses growing in my potager


What does sp. stand for? I found this very useful article by Susan Mahr about Botanical and Latin names. I learned that:

Unspecified or unknown specie in the genus of for instance Salvia would be written as Salvia sp. To signify more than one species in the genus,