Absolute episode numbering.
The standard for this site is the the primary episode number is representative of the shows aired order. But as any Anime fan will tell you Anime episodes are usually numbered without seasons and go from episode 1 to whatever the final episode is, often into the hundreds. Most western broadcasters however do break these shows into seasons, so in order to accommodate this alternate numbering scheme an additional field Absolute Number is available. While this system is primarily intended for Anime series that don't really have seasons, it will work for any program.
To use this interface there is no alternate season number only the absolute episode number. Numbering continues on from season to season. So if season 1 ends with 25 then season 2 begins with 26. So for example Bleach is currently in it's "sixth season" but season 5 episode 14 Shock! The Father's True Character is actually episode 111.