If the card had too many holes in it, it wouldn't be there. Use the idea of a collection of holes edge-to-edge across the lens to describe what you would see as the screen was moved closer and farther away. What would all the patterns look like when the screen wasn't at the focus position?

 

Pinhole pattern and lens Turn off your light, poke more holes in your card and use it to cover up a lens as shown here so that light from the bulb will pass through both the holes and the lens before it strikes the screen.