363 is over the 350 line so it is rounded to 400 its like a number line from one to ten 1 2 3 4 5. 6 7 8 9 10 ... where is 2 close to? The start 1 or 10? 1 right? Another one... where is 7 close to? 10 right because it is nearest to 10 and has passed 5 ! Hope this helped x
