The problem is that inside your web.config your default size for the file is set to be 4mb (4mb is default, so even if there is no settings set then 4mb size would be define as the value for maxRequestSize attribute of the HttpRunTime).
A solution to this would, be, to change that value and update it to make it of your own choice.
Following shows an example of that, you can definitely add more attributes to create (or maintain or update) your configuration of the website in IIS.
<configuration>
<system.web>
<httpruntime maxrequestlength="100000" />
</system.web>
</configuration>
Note: The file size in above method is 100mb (less than that of course because an MB is of 1024kb not 1000kb), size defined is in kilobytes. For more on this, please read this documentation.
https://msdn.microsoft.com/en-us/library/e1f13641%28v=vs.71%29.aspx