Sep 25, 2014 03:15 AM|smirnov|LINK
1Mb is 1024Kb each 1024bytes
It's not that important to have 31457280 or 30000000. Even Microsoft set default value of 30000000
Also that is a limit of a whole request not a single file which you want to upload and request will be always bigger because it includes form variables, view state, etc. So, if your requirement is to have a file of 30Mb then set limit bigger than 30, e.g. 30500000
and test if it works.