well let us say the current bid is 400 by Mr. X but Mr. X has put in a max bid of 800 so you come along and see the auction at 400 and bid 450 Mr.X's max bid will automatically bid 451 for him and keep doing so till his max of 800 is reached so depending on how high the current winner placed the max it may take a wile to out bid him. I know some people who will bid 3000 on a 100 credit auction to try to ensure they win that can get annoying sometimes
Also, once a bid is placed, you can't change the conditions of the auction (for example: the number of days it's listed). In this case, xxh0wlw0lfxx, the first bid was placed by meganmgresham at 11:50:19 AM EST on Nov 23rd 2011, a day and a half BEFORE you asked for lower days.