Hmmmmmm.
Professor Kokonoe is right: it looks like the level of the spell is a simple typo. All printed versions that I can find are 4th level. I'm editing the guide to reflect this.
The version I was looking at was the Player's Guide to Faerun version, p. 112:
Spell Enhancer
Transmutation
Level: Sorcerer/wizard 4
Components: V
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: 1 round
This spell enhances the next spell you cast, making it more difficult for targets to resist. After you cast this spell, you can cast another in the same round (as if it had been quickened) at +2 caster level.
I would personally read 'as if it had been quickened' to mean that the spell would have to meet normal requirements for Quicken Spell, which is to say that it can't have a casting time of more than a full-round action. Or two full-round actions, if you're using Arcane Spellsurge. Or 2-10 full-round actions, if you're using Rapid Spell. Or any casting time, if you're using Uncanny Forethought.
If you're playing with a GM who's strict about the 'later-printed versions of spells supersede earlier-written versions' thing, this makes it moot.