When Penny brings Leonard wine she only pours one glass, but when she walks away the second glass, which she picks up and bring with her, is also filled.
When we first see the three whiteboards, the left board has red ink on it but when Leonard visits Sheldon, the board has black ink on it.
But there is no way to know how much time has passed, so he could have erased and changed it all. He was working all day.
But there is no way to know how much time has passed, so he could have erased and changed it all. He was working all day.