Just finished watching the HOH comp again and here is a second by second recap of what happened.
(I will use 0:00 as the time Julie started reading the question)
0:00 - Julie reads the question
0:15 - Julie starts saying "Houseguests... I need your answers"
0:17 - Beau and Janelle BOTH begin movement of their cards
0:18 - Beau's answer of 175 is visable
0:20 - Janelle's upside down 300 is visable
0:22 - "Janelle, you are upside down."
0:26 - Janelle flips her card over, showing second answer
0:30 - April finally finishes with 145
0:35 - Janelle raises her card in victory even though Julie has not announced the winner
0:38 - Janelle holds card down, looks to her right and smiles to someone off-camera
0:40 - Janelle wins HOH
You can say what you want, but the fact is Janelle showed 300, 5 seconds AFTER Julie asked for answers, and then showed 275 a full 16 seconds after Julie asked for answers