World
1945: German Me 262 jet fighters shoots [sic] down 10 U.S. bombers near Berlin

Some googling leads me to several possible answers: (1) The Me-262 was the world's first jet aircraft, (2) losing ten bombers on a single day may have been a very high one-day loss, (3) maybe whoever chose this factoid simply wanted to note that the Germans still had it together enough at such a late date to manage to shoot down ten in one go-'round
On #2: According to this, the U.S. 8th Air Force, which flew bombers against Germany, lost 4,145 bombers in the war.
The 8th flew Mission #1 on 17 August 1942 when 12 B-17s attacked Rouen Marshalling yards and the last mission on 8 May 1945 Mission #986, when 12 B-17s dropped leaflets in Germany.