Curtains: AI - 67 chip bubble raise

[45suited]

What is the reasoning behind this less than AI raise? Is it so, if bigstack pushes, but then one of the two shorter stacks picks up a hand, they can't call because if they do, you can fold and make ITM with your few remaining chips? This less than AI raise then would help to ensure that you get heads up with bigstack if he overpushes?

PartyPoker, Big Blind is t300 (4 handed) Converter on pregopoker.com

Hero (t1367)
Button (t4645)
SB (t2300)
BB (t1688)

Preflop: Hero is in UTG with 2[img]/images/graemlins/club.gif[/img] 2[img]/images/graemlins/spade.gif[/img]
<font color="red">Hero raises t1300</font>, <font color="gray">Button folds</font>, <font color="gray">SB folds</font>, <font color="gray">BB folds</font>