|2d6||Base Cost||3rd Level||5th Level|
The columns are rated by level. Since it's really easy to double a number, the even numbered levels were skipped: double the base cost for researching a second level spell, for example.
Spells are the main thing that are rated by level, but a few other things could be, too. For example, unusual hirelings might have level ratings. Digging for information about something that has a level rating -- villain, dungeon level -- might be equivalent to half the target's rating, so an eyewitness account of someone who's been to the fifth level of the Scary Dungeon might be 2nd level information. Things that cause damage are effectively one level per dice of damage. Most non-magical things, however, will all be lumped together as 1st level.