Thankyou Stevie for having the balls to say what a lot of members on this site are thinking, but are too scared to write. There is no need for you to say sorry, you have done nothing wrong. Yes, your comment may be considered to some as a little "nit picky", but it is ok to post those opinions on these boards - after all that's what this forum is for. I believe most members on this site are mature enough to understand that your comment as a whole was positive. And that you are someone who appreciates detailed theming and consistency in storyline.
I think @New display name has the right idea. The logic is that the TNT inside the shed has exploded, causing the tin to deform outwards.