[Kaitel]

If he made sure he was staying he knew it would be at the expense of Charlie going, who he obviously has a crush on, and she'd feel betrayed that way then. But he didn't wanna go either, so he went high while still giving room in the hopes maybe each board had been different or whatever. They claim not to care about the money so why they get so upset if he had it anyway? They left Dexter with a tough choice, get evicted or force Charlie out for an even higher amount of the prize fund, so he just picked a number he had in his mind already.