Taking a chance

I took a punt on this lovely 1000 piece puzzle in a charity shop for £1.49. I decided to count the pieces before I started, there were 1005. Fine, I thought. “That doesn’t sound quite enough” said my other half. “Factors” he said. “There should be 1008 pieces.” Having completed the puzzle there are exactly 3 pieces missing. Which proves (a) Ross knows his maths and (b) I am a very accurate jigsaw-piece counter. And I always thought a 1000 piece jigsaw had 1000 pieces - who knew?!