Rick Riordan said this quote

I’ll be back with the sandwiches,” she said. “But I had some leftover seven-layer dip.”“Yum.” Percy dug in with a tortilla chip. “She’s kinda famous for this, guys.”Sally ruffled his hair. “There’s guacamole, sour cream, refried beans, salsa—”“Seven layers?” I looked up in wonder. “You knew seven is my sacred number? You invented this for me?”Sally wiped her hands on her apron. “Well, actually, I can’t take credit—”“You are too modest!” I tried some of the dip. It tasted almost as good as ambrosia nachos. “You will have immortal fame for this, Sally Jackson!