Blonde and a Brunette walk into a bar

A blonde and a brunette walk into a bar. The brunette tells the bartender, “I’ll have a screwdriver” The blonde asks her, “What is that?” The brunette says, “Well it’s a vodka and orange” The blonde thinks for a moment and then exclaims, “Alright, I’ll have a 15” The brunette puzzled by this asks, “What?” The blonde replies, “Oh you know, a seven and seven”