What value do I put in the Forum Permissions / Maximum size of file attachments / Admin _____

The note says 2M max file size . I want to use the max files size. So what value do I put in to achive this??

The 2MB limit is from your pkp.ini setting your host has.
So you can't exceed that limit unless the host allows you to.
In the ubb control panel the setting is in bytes. So for 1 MB you would enter 1048576. For 2MB it would be 2097152

Ah...I was setting 2000 and it was still saying file was to large 2MB max. I used the wrong conversion.

The ubb script will use whichever is the smaller setting between your php.ini and the ubb setting.
So 2000 is very small.