ALL USED CDs & DVDs BUY 2 GET 1 FREE for the rest of June!
SImple enough, right? Items are grouped in order of price, every third one is free. So if you bought stuff that was $10, $10, $10, $5, $4, $1 - the $10 one and $1 one would be free. Hope that makes things clearer and sin't confusing.