What can I do in FRA for 10 Hours....

[The High Flyer]

They stamped my passport again and put a cross on top of it...Because of this...french immigration in gare du nord questioned me about the cross...which I didn't have single clue why did that happens....but then he let me proceed after held me for more than 15 min...

I might be missing something, but what does a cross on the stamp mean?